Earthquakes. Earthquakes

Transcription

1 Earthquakes Profiling Hazard Event An earthquake happens when two blocks of the earth suddenly slip past one another, releasing built-up energy. The surface between these two blocks of earth is referred to as a fault or fault plane. When these blocks move, they produce seismic waves that are transmitted through the rock outwardly in all directions producing ground shaking. Earthquakes are unique multihazard events with the potential to cause huge amounts of damage and Figure2D-1 Earthquake Frequency loss. Secondary geological effects due to ground shaking include: surface fault rupture, liquefaction and lateral spreading, seiches, tectonic subsidence, landslides, and rock falls. Ground shaking can also impact the built environment resulting in fires, possible dam failures, infrastructure damage, hazardous material releases and building damage. The Intermountain Seismic Belt Utah straddles the physiographic region boundary between the extending Basin and Range Province to the west and the relatively stable Rocky Mountains and the Colorado Plateau to the east. This boundary coincides with an area of earthquake activity called the Intermountain Seismic Belt (ISB). The ISB is a zone of pronounced earthquake activity up to 120 miles wide extending in a north south direction 800 miles from Canada to northern Arizona and eastern Nevada. Utah s longest and most active fault, the Wasatch fault, lies within the ISB. Unfortunately, the heavily populated Wasatch Front (Ogden- Salt Lake City-Provo urban corridor) and the rapidly growing St. George-Cedar City areas are also with the ISB putting most of Utah s residents at risk (Utah Safety Seismic Commission). Earthquake Hazards In addition to ground shaking, this section will discuss the various geological hazards that may accompany earthquakes, including: surface fault rupture, liquefaction and lateral spreading, tectonic subsidence, types slope failure, and various types of flooding. Other sections discuss non-earthquake induced landslides and flooding. Ground Shaking Ground shaking causes the most impact during an earthquake because it affects large areas and is the origin of many secondary effects associated with earthquakes. Ground shaking, which generally lasts 10 to 30 seconds in large, normal-faulting earthquakes, is caused by the passage of seismic waves generated by earthquakes. Page 87

2 Earthquakes produce both vertical and horizontal ground shaking as illustrated in figure 2D-2. The primary or P waves are compressional; the secondary or S waves have a shear motion. These body waves radiate outwards from the fault to the ground surface where they cause ground shaking. The fast moving P waves are the first waves to cause the vibration of a building. The S waves arrive next, often causing a structure to vibrate from side to side. Surface waves, characterized as Rayleigh (R) and Love (L) waves, arrive last, causing low-frequency vibrations. Surface waves are more likely than P and S waves to cause tall buildings to vibrate. Earthquake waves vary in both frequency and amplitude. High frequency low amplitude waves trigger more damage to short, stiff structures, where low frequency high amplitude waves have a greater effect on tall (high-rise) structures. Ground shaking is measured using Peak Ground Acceleration (PGA). The PGA measures the rate in change of motion relative to the established acceleration due to gravity. Earthquakes generate seismic waves at a wide variety of frequencies, and frequency waves may be amplified by local conditions. In the Salt Lake Valley, areas with thick, soft, clayey soil amplify lowfrequency seismic waves, yielding slow rolling-type shaking that can damage tall buildings and long span overpasses. Areas with thin, stiff (sandy and gravelly) soil over bedrock amplify high-frequency seismic Figure 2D-3 Wasatch Fault block model. Courtesy of UGS Figure 2D-2 Seismic waves Courtesy of DCEM waves, which yield vigorous ground vibrations that cause more damage to short (1-2 story) buildings, such as houses (Utah Safety Seismic Commission). Surface Fault Rupture During a large earthquake when the two blocks of the earth suddenly slip past one another along the fault plane, the result may be a surface fault rupture, also referred to as a fault scarp. The surface rupture of a steeply dipping fault plane may result in the formation of large fault scarps. Surface fault rupture along the Wasatch fault is expected for earthquakes with magnitudes of 6.5 or larger. The largest credible earthquake that may strike Utah is estimated to be a magnitude 7.0 to 7.5 and is likely occur on the Wasatch Fault. An earthquake of this magnitude, based on current research, would create a fault scarp causing a displacement of roughly 6 to 10 feet in height and miles long. Historically, a surface fault rupture has only occurred once in Utah; Page 88

3 the 1934 Hansel Valley earthquake with a magnitude 6.6 produced 1.6 feet of vertical offset. Surface fault rupture does not always occur on a single distinct plane. It may occur over a zone several hundred feet wide known as the zone of deformation. The zone of deformation occurs mainly on the downthrown side of the main fault trace. Frequently, antithetic faults form, moving in the opposite direction of the main fault, creating grabens (down dropped blocks) within the zone of deformation. This is called tectonic subsidence. Surface fault rupture and the zone of deformation present significant challenges to the built environment. Anything built on, near, or crossing the fault has a high potential of being significantly damaged. Foundations will be cracked, buildings torn apart, and roads, utility lines, pipelines, and other lifelines will be disrupted. Figure 2D-4 Displacement in excavation Courtesy of UGS Liquefaction Soil liquefaction occurs when watersaturated, disintegrated sandy soils are subject to ground shaking. When liquefaction occurs, soils behave more like a viscous liquid (quicksand) and lose their bearing capacity and shear strength. Two conditions must be met in order for soils to liquefy: (1) the soils must be susceptible to liquefaction (sandy, loose, water-saturated soils typically between 0 and 30 feet below the ground surface) (2) ground shaking must be strong enough to cause susceptible soils to liquefy. The loss of shear strength and bearing capacity due to liquefaction causes buildings to settle or tip, and light buoyant structures such as buried storage tanks and empty swimming pools to float upward. Liquefaction can occur during earthquakes of magnitude 5.0 or greater. Recently, liquefaction features were found in the 2010 M4.9 Randolph Earthquake in Rich County. Lateral Spread Soils, once liquefied, can flow on slopes with angles of 0.5 to 5 percent. This movement of liquefied soils is known as lateral spread. "The surficial soil layers break up and sections move independently, and are displaced laterally over a liquefied layer" (Eldredge 10). Liquefaction can cause damage in several ways, with lateral spreading occurring the most. Displacement of three (3) or more feet may occur and may be accompanied by ground cracking and vertical displacement. Lateral spreading causes roads, buildings, buried utilities, and any other buried or surface structure to be either compressed or pulled apart. Page 89

4 Various Flooding Issues Related to Earthquakes Earthquakes could cause flooding due to regional lowering and tilting of the valley floor (tectonic subsidence), dam failure or seiches in lakes and reservoirs. Flooding can also result from the disruption of rivers and streams. Water tanks, pipelines, and aqueducts may be ruptured, or canals and streams altered by ground shaking, surface faulting, ground tilting, and landsliding. Page 90 Earthquakes Figure 2D-5 Comparison between MMI and RM Courtesy of DCEM Earthquake Measurement An earthquake s size can be measured in several ways. One way is by magnitude, a measure of the energy released. The second is by intensity, a measure of the strength of ground shaking at a particular point that varies by location, proximity to the sour of the earthquake, and type of material underlying the site. The Richter Magnitude scale, a logarithmic scale where every whole number increase represents a ten-fold increase in recorded ground motion, is used to measure magnitude. The Modified Mercalli Intensity (MMI) Scale is a descriptive scale that ranges from low (I) to high (XII). Seiches Standing bodies of water are Figure 2D-6 Segments of Wasatch Front susceptible to earthquake ground motion. Water in lakes and reservoirs may be set in motion and slosh from one end to the other, much like in a bathtub. This motion is called a seiche (pronounced saysh ). A seiche may lead to dam failure or damage along shorelines. Slope Failure Earthquake-induced landslides, rock falls and other types of slope failure could be triggered by ground shaking. Slope failure is usually confined to mountainous or canyon areas, however, steep ravines and slopes within city limits could also experience slope

5 failure. The extent of slope failure depends upon the severity of ground shaking, steepness of slope, moisture content, and type of soil or rock. If the earthquake occurs in the winter months, snow avalanches may constitute the greatest slope failure hazard. Significant Earthquakes: Every year, seismograph stations record about 700 earthquakes occurring in Utah. Most of these earthquakes are too small to even be felt. Figure I-43 demonstrates the average frequency of earthquakes in Utah. Utah has numerous active faults throughout the state capable of causing damage, but due to the number of people residing along the Wasatch Front and the amount of infrastructure, an event on the Wasatch Fault would cause the most damage. Table 2D-1 provides a timeline of all earthquakes larger than 5.0 magnitude, occurring in Utah from 1876 to present. Table 2D-1 Significant Utah Earthquakes Date Name Magnitude Intensity March 22, 1876 Moroni 5.0 VI December 5, 1887 Kanab 5.7 VII April 20, 1891 St. George 5.0 VI July 18, 1894 Ogden 5.0 VI August 1, 1900 Eureka 5.0 +/-.5 VII November 13, 1901 Southern Utah 6.0 +/-.5 IX November 17, 1902 Pine Valley 6.0 VIII April 15, 1908 Milford 5.0 VI October 5, 1909 Hansel Valley 6.0 VIII January 10, 1910 Elsinore 5.0 VI May 22, 1910 Salt Lake City 5.5 VII May 13, 1914 Ogden 5.0 +/-.5 VII July 15, 1915 Provo 5.0 VI September 29, 1921 Elsinore 6.0 VIII January 20, 1933 Parowan 5.0 VI March 12, 1934 Hansel Valley 6.6 IX August 30, 1942 Cedar City 5.0 VI September 26, 1942 Cedar City 5.0 VI February 22, 1943 Magna 5.0 VI November 17, 1945 Glenwood 5.0 VI March 6, 1949 Salt Lake City 5.0 VI February 13, 1958 Wallsburg 5.0 VI February 27, 1959 Panguitch 5.0 VI July 21, 1959 Southwest 5.7 VI April 15, 1961 Ephraim 5.0 VI August 30, 1962 Cache Valley 5.7 VII September 5, 1962 Magna 5.2 VI October 4, 1967 Marysvale 5.2 VII March 27, 1975 Pocatello Valley, ID* 6.0 VIII August 14, 1988 San Rafael Swell 5.3 VI January 29, 1989 Wasatch Plateau 5.4 VI September 2, 1992 St. George 5.8 VII *Occurred in Idaho, felt in throughout northern Utah; Table derived from information provided by the University of Utah Seismograph Stations Page 91

6 Illustrated in Figures 2D-7 2D-12 are the location of earthquakes from 1850 through 2011 larger than 3.0. These maps provide spatial reference to seismically active areas Figure 2D-7 Earthquake Epicenters *Epicenters represented here are derived from the historic catalog at the University of Utah Seismograph Stations database. The year 1850 represents the year of the first publication of a newspaper in the state of Utah. Page 92

7 Figure 2D-8 Earthquake Epicenters in Utah Earthquakes Page 93

8 Figure 2D-9 Earthquake Epicenters in Utah *Magnitudes of earthquakes occurring after 1981 have been revised by the University of Utah Seismograph Stations as noted at: Page 94

9 Figure 2D-10 Earthquake Epicenters in Utah Earthquakes *Magnitudes of earthquakes occurring after 1981 have been revised by the University of Utah Seismograph Stations as noted at: Page 95

10 Figure 2D-11 Earthquake Epicenters in Utah Earthquakes *Magnitudes of earthquakes occurring after 1981 have been revised by the University of Utah Seismograph Stations as noted at: Page 96

11 Figure 2D-12 Earthquake Epicenters in Utah Earthquakes *Magnitudes of earthquakes occurring after 1981 have been revised by the University of Utah Seismograph Stations as noted at: Page 97

12 Figure 2D-13 Historical & Instrumental Seismicity in Utah ( ) Source: University of Utah Seismograph Stations earthquake catalog (number of earthquakes = 44,634) Page 98

13 Figure 2D-14 Utah Quaternary Fault Map Utah Geological Survey Page 99

14 Figure 2D-15 Peak Acceleration (%g) with a Probability of Exceedance in 50 Years Source: The U.S. Geological Survey (USGS) developed and periodically updates its National Seismic Hazard Maps. These maps illustrate probabilistic ground motion for PGA and various spectral accelerations (SA). The standard for evaluating the ground motion hazard is a 2% in 50 year probability of exceedance for PGA. The PGA values applicable to Utah are shown on the following map. The contour values show the probabilistic ground motions expressed in a percentage of gravity. It must be noted that there are limitations to these hazards maps. The maps are based only on data from published faults. There may be many more faults that could contribute to the ground motion hazard that are not currently reflected on the maps. Figures 2D-7-15 show that the areas of the state that have experienced the most earthquakes and are at the greatest risk to earthquakes include the Logan Metro Area, the Page 100

15 Ogden-Salt Lake-Provo Metro Area, the Cedar City Metro Area and the St. George Metro Area. The ground motions in these are Metro Areas may be perceived as strong to severe (violent) with light to heavy damage potential. The maps highlight that the areas where Utah experiences the most earthquakes are the most populated regions of the state and generally follow the I-15 corridor. These areas are population centers and are experiencing some of the greatest growth in the state. Without earthquake mitigation which goes beyond adopting current and future building codes to lesson or eliminate the effects of ground motion on the built environment, the potential losses will increase as population growth, building and development expands. Assessing Vulnerability by Jurisdiction Earthquakes will continue to occur in Utah. The precise time, location and magnitude of future earthquakes cannot be predicted. Earthquake hazard areas in Utah are concentrated along the Intermountain Seismic Belt (ISB). The ISB is a zone of pronounced earthquake activity up to 120 miles wide extending in a north south direction 800 miles from Canada to northern Arizona and eastern Nevada. Utah s longest and most active fault, the Wasatch fault, lies within the ISB. The heavily populated Wasatch Front (Ogden-Salt Lake City-Provo urban corridor) and the rapidly growing St. George-Cedar City areas are also with the ISB putting most of Utah s residents at risk. (USSC) Numerous factors contribute to determining areas of vulnerability. Key factors include historical earthquake activity, proximity to faults, soil characteristics, building construction, and population density. Earthquake Hazard Areas The USGS developed earthquake hazard maps showing ground acceleration for the United States. The peak acceleration values applicable to Utah are shown in Figure 2D- 15. The contour values show the earthquake ground motions with acceleration expressed as a percentage of the acceleration of gravity with a two-percent probability of being exceeded in fifty years. Areas of the state that are at risk to the seismic hazard include the Logan Metro Area, the Ogden-Salt Lake-Provo Metro Area, the Cedar City Metro Area and the St. George Metro Area. The ground motions in these are Metro Areas may be perceived as strong to severe (violent) with light to heavy damage potential. These areas are population centers and are experiencing some of the greatest growth in the State. Without earthquake mitigation which goes beyond adopting current and future building codes to lesson or eliminate the effects of ground motion on the built environment, the potential losses will increase as population growth, building and development expands. Page 101

16 County vulnerability ranking is based on HAZUS earthquake data (see below) from Tables 2D-3-6. These data include the total direct economic losses and per capita losses from buildings based on annualized loss analysis and the direct economic and per capita losses from HAZUS earthquake scenarios (see below). All 29 counties were given a ranking (1-29) for each of the 4 criteria (from Tables 2D-3-6) and then summed to determine a vulnerability number for every county. Those with highest combined ranking (i.e. the lowest number) were considered the most vulnerable. For example, if a county was ranked 1 for each of the four criteria then it would receive a 4 vulnerability number and would rank as the most vulnerable. The following counties are ranked from most vulnerable to least vulnerable based on the above assessment: 1. Salt Lake 2. Davis 3. Weber 4. Utah 5. Box Elder 6. Cache 7. Iron 8. Tooele 9. Washington 10. Juab 11. Sevier 12. Wasatch 13. Summit 14. Sanpete 15. Garfield 16. Beaver 17. Rich 18. Millard 19. Piute 20. Carbon 21. Morgan 22. Emery 23. Duchesne 24. Kane 25. Uintah 26. Daggett 27. Wayne 28. Grand 29. San Juan Estimating Potential Losses by Jurisdiction The Utah Division of Emergency Management (DEM) created a statewide HAZUS study region to perform an average annualized loss (AAL) analysis. The HAZUS Earthquake Module User Manual defines annualized loss as: the expected value of loss in any one year, and is developed by aggregated the losses and their exceedance probabilities (FEMA, HAZUS-MH 2.1 Earthquake User Manual, pg. 9-1). An AAL analysis allows DEM to examine losses across the state both in terms of total expected loss per year as well as per capita loss per year. HAZUS produces two primary outputs in an AAL analysis: the Direct Economic Loss for Buildings as well as the number of casualties in each county. The casualty counts are shown based on the four HAZUS severity levels: 1.) Injuries requiring medical attention 2.) Injuries requiring hospitalization that are non-life threatening 3.) Injuries requiring hospitalization that could become life-threatening if not properly treated 4.) Deaths The casualty counts are shown for three different scenarios in each county: 2 a.m.-- a nighttime scenario where HAZUS assumes most people are at home, 2 p.m. -- a daytime scenario where HAZUS assumes most people are at work and 5 p.m. -- a commuting scenario where HAZUS assumes that many people will be commuting from work to their homes. Page 102

17 HAZUS reports casualties for the three different scenarios and injury severity levels based on the expected casualties by six different building classes: commercial, educational, hotels, industrial, other-residential and single family residences. HAZUS also estimates casualties for persons commuting. The casualty results from the HAZUS AAL run are shown in Appendix R. The highest total number of casualties in all severity levels occurs in Salt Lake County in a 2 a.m. scenario: 144. Salt Lake County also has the highest estimated casualties in a 2 p.m. scenario (105) and a commuting scenario (106). One interesting trend in casualties is that Davis, Utah and Weber Counties have a higher number of casualties in a 2 p.m. scenario (28, 34 and 29, respectively) than they do in a 2 a.m. scenario (19, 17 and 24, respectively). HAZUS estimates zero annual casualties from earthquake for the following counties: Beaver, Carbon, Daggett, Duchesne, Emery, Garfield, Grand, Juab, Kane, Millard, Morgan, Piute, Rich, San Juan, Summit, Uintah, and Wayne. HAZUS estimates fewer than five total annual casualties across all severity levels from earthquake in all three scenarios for the following counties: Iron, Sanpete, Sevier, Tooele, Wasatch, and Washington. HAZUS estimates eight total annual casualties across all severity levels from earthquake in all three scenarios for Box Elder County and twelve casualties for Cache County. The second primary output from an AAL analysis is the Direct Economic Losses for Buildings. These results are shown in Table 2D-2, 2D-3 and 2D-4. There are nine counties where HAZUS estimates more than $1,000,000 in annual direct economic losses: Box Elder, Cache, Davis, Iron, Salt Lake, Tooele, Utah, Washington and Weber. As part of our AAL analysis, we calculated the per capita direct economic losses by dividing the total direct economic losses by the 2010 Census population for each county. Salt Lake County had the highest total direct economic losses ($124,607,000) and the highest per capita losses ($121.02). Weber County was the only other county aside from Salt Lake with higher than $100 per capita losses ($113.69). The per capita losses highlighted at least one instance of rural earthquake risk that was not apparent in total loss numbers. The AAL analysis reported $191,000 of total loss for Rich County in the northeast corner of the state. The per capita loss for Rich County was $84.36, which is a higher per capita loss than six of the nine counties that HAZUS estimates over $1,000,000 in losses per year. The total direct economic loss for buildings is shown in Figure 2D-16 while the per capita direct economic loss for buildings is shown in Figure 2D-17. Page 103

18 Table 2D-2 Earthquakes Page 104

19 Table 2D-3 HAZUS Earthquake Losses for Buildings by County (from Table 2D-2)) County Loss Estimates - FEMA HAZUS EARTHQUAKE Direct Economic Losses For Buildings* Building Damage Non-Structural Damage Total $$ loss (most to least) Salt Lake $17,774,000 $56,062,000 $124,607,000 Utah $3,975,000 $15,303,000 $31,730,000 Davis $3,929,000 $13,354,000 $26,392,000 Weber $3,806,000 $12,993,000 $26,290,000 Cache $841,000 $3,029,000 $6,395,000 Box Elder $481,000 $1,497,000 $3,095,000 Tooele $271,000 $881,000 $1,767,000 Washington $221,000 $826,000 $1,686,000 Iron $176,000 $656,000 $1,357,000 Wasatch $141,000 $444,000 $968,000 Sanpete $120,000 $376,000 $843,000 Summit $111,000 $425,000 $798,000 Sevier $116,000 $342,000 $736,000 Juab $54,000 $173,000 $402,000 Carbon $63,000 $174,000 $388,000 Millard $48,000 $132,000 $298,000 Beaver $31,000 $96,000 $235,000 Garfield $26,000 $91,000 $228,000 Rich $30,000 $97,000 $191,000 Duchesne $23,000 $69,000 $152,000 Uintah $21,000 $64,000 $139,000 Emery $21,000 $61,000 $132,000 Kane $18,000 $53,000 $119,000 Piute $14,000 $39,000 $82,000 Morgan $11,000 $33,000 $67,000 Grand $6,000 $14,000 $34,000 San Juan $3,000 $9,000 $22,000 Wayne $3,000 $9,000 $20,000 Daggett $2,000 $5,000 $11,000 State of Utah $32,336,000 $107,307,000 $229,184,000 Totals only reflect data for those census tracts/blocks included in the user s study region and will reflect the entire county/state only if all of the census blocks for that county/states were selected at the time of study region creation. Source: FEMA Region VIII; 2014; *See Appendix R for a full breakdown of all the direct economic loss numbers. Page 105

20 Figure 2D-16 Combined Estimated HAZUS Earthquake Annualized Losses by County Page 106

21 Table 2D-4 Total Earthquake Per Capita Losses for Buildings by County (from Table 2D-2) Rank County Per Capita Total Loss from HAZUS Earthquake 1 Salt Lake $ Weber $ Davis $ Rich $ Box Elder $ Utah $ Cache $ Piute $ Garfield $ Wasatch $ Juab $ Beaver $ Sevier $ Tooele $ Sanpete $ Iron $ Millard $ Summit $ Carbon $ Kane $ Washington $ Emery $ Daggett $ Duchesne $ Wayne $ Morgan $ Uintah $ Grand $ San Juan $1.49 Source: FEMA Region VIII; 2014; Population 2010 census, census.gov Page 107

22 Figure 2D-17 Combined Estimated HAZUS Earthquake Per Capita Losses by County Page 108

23 Utah HAZUS Scenario Analysis Since 2008, DEM has worked with FEMA Region VIII, the University of Utah Seismograph Stations and the Utah Geological Survey to develop credible earthquake scenarios for active faults around the State. The results of the initial work on these scenarios are available at: The scenarios represent both maximum credible events on as well as historic events and these faults. To date, there are twenty scenarios of which four represent historic events. The current HAZUS scenarios are: Anderson Junction Segment, Hurricane Fault -- M 7.4 Ash Creek Segment, Hurricane Fault -- M 6.9 Bountiful epicenter, Weber Segment, Wasatch Fault -- M 6.5 Brigham City Segment, Wasatch Fault -- M 7.0 Cache Valley -- Historic Event, East Cache Fault -- M 5.7 Cedar City Segment, Hurricane Fault -- M 6.6 Collinston Segment, Wasatch Fault -- M 6.8 Great Salt Lake epicenter, Antelope Island Segment, East Great Salt Lake Fault -- M 7.0 Hansel Valley -- Historic Event, Hansel Valley Fault -- M 6.6 Magna -- Historic Event, M 5.2 Nephi Segment, Wasatch Fault -- M 6.9 Ogden epicenter, Weber Segment, Wasatch Fault -- M 6.5 Provo Segment, Wasatch Fault -- M 7.2 Richfield -- Historic Event, M 6.5 Salt Lake City Segment, Wasatch Fault -- M 7.0 San Rafael Swell -- M 5.3 Taylorsville -- M 6.0 Tooele County -- M 6.5 Washington Fault -- M 6.5 Weber Segment, Wasatch Fault -- M 7.0 FEMA Region VIII has performed a number of updates to available HAZUS data since the 2011 State Hazard Mitigation Plan. Most of this work occurred on the Salt Lake City Segment M 7.0 scenario which represents the most catastrophic credible event (in terms of economic loss) in the state. These updates include: using a finite-fault earthquake scenario, using Salt Lake County Assessor s Office building stock data, 2010 Census demographics, 2012 RS Means valuations and 2011 HSIP data. This work occurred during the preparation for both the ShakeOut 2012 full-scale exercise and the ShakeOut 2013 functional exercise. USGS ShakeMaps HAZUS uses USGS ShakeMaps as inputs for actual events as well as scenario events. The University of Utah Seismograph Stations developed all of the ShakeMaps used in the twenty scenarios we analyzed. The default ShakeMap input for HAZUS is a series of Page 109

24 files showing average ground accelerations. Since the ShakeOut 2013 exercise, FEMA Region VIII has updated the Salt Lake City Segment scenario using maximum direction (or peak) ground acceleration. DEM concurs with FEMA Region VIII that the above data enhancements and use of PGA represent the best loss estimates based on current scientific knowledge. A ShakeMap depicts the intensity of ground shaking produced by an earthquake based on the intensities measured by seismographs. A ShakeMap consists of several products that can be viewed and analyzed using any geographic information system (GIS) software. These products are: PGA, peak ground velocity (PGV), the response spectra at 0.3 and 1.0 seconds (useful for analyzing the effect of the earthquake on buildings in the region) and an intensity map showing ground shaking on a MMI scale. The MMI map depicts the intensity of ground shaking with warmer colors indicating higher ground shaking levels and cooler colors indicating lower ground shaking levels. These colors are related to PGA and PGV in the image below: Image: U.S. Geological Survey: The MMI scale is useful for communicating potential earthquake damage to a broad audience because it correlates measured intensities (as in the above image) with what a person may actually feel. For a more complete description of the MMI scale and potential damages based on intensity levels, please see this page: In a scenario ShakeMap is generated by assuming an earthquake of a particular magnitude occurring on a specified fault. A scenario ShakeMap shows realistic ground shaking intensities based on these assumptions. For a complete discussion on scenario ShakeMaps, please see this page: Utah Scenario Earthquake Analysis For the 2014 State Hazard Mitigation Plan (SHMP), the only scenario that has been updated with all of the data enhancements and use of PGA is the Salt Lake City Segment M 7.0. In subsequent updates to the SHMP, DEM will update all of the other scenarios to reflect current data and scientific knowledge. The ShakeMaps for all twenty of the current scenarios are shown in Appendix R. Page 110

25 DEM created a county-by-county table (Table 2D-5) of estimated Direct Economic Loss for Buildings showing losses for each of the twenty scenarios. There are fourteen counties that have at least one scenario producing $1,000,000 or more in Direct Economic Losses: Box Elder, Cache, Davis, Iron, Juab, Salt Lake, Sanpete, Sevier, Summit, Tooele, Utah, Wasatch, Washington and Weber. The Salt Lake City Segment M 7.0 scenario produces the maximum losses in three counties: Salt Lake (over $27,000,000,000), Summit (over $33,000,000) and Wasatch (over $12,000,000). There are five counties with over $1,000,000,000 in loss potential: Davis, Salt Lake, Utah, Washington and Weber. There are six scenarios that produce at least $1,000,000,000 of Direct Economic Loss in Salt Lake County: Bountiful -- M 6.5, East Great Salt Lake Fault -- M 7.0, Provo Segment -- M 7.2, Salt Lake City Segment -- M 7.0, Taylorsville -- M 6.0 and the Weber Segment -- M 7.0. In total, Salt Lake County has a loss potential of over $42,000,000,000 across all twenty scenarios. The five counties with the highest total Direct Economic Losses for all scenarios are (in order): Salt Lake, Davis, Utah, Weber and Washington. The five counties with the highest total per capita Direct Economic Loss for all scenarios are (in order): Salt Lake, Davis, Weber, Utah and Box Elder. While Washington County has over $1,000,000,000 in Direct Economic Loss potential, its per capita losses are only $8,302, which is the lowest of the five counties with such a high loss potential. Three counties had a higher per capita loss potential than Washington County with lower total loss potential: Box Elder ($17,911 per capita, over $895,000,000 total), Iron ($15,278 per capita, over $705,000,000 total) and Juab ($10,436 per capita, over $106,000,000 total). There are four counties that did not have any Direct Economic Losses in any of the twenty scenarios: Daggett, Grand, San Juan and Wayne. Including these four counties, there are a total of nine counties whose total loss potential is less than $1,000,000: Daggett, Duchesne, Grand, Kane, Piute, Rich, San Juan, Uintah and Wayne. A map showing total loss potential for all scenarios by county is shown in Figure 2D-18. A map showing per capita loss potential for all scenarios by county is shown in Figure 2D-19. Page 111

26 Table 2D-5 Direct Economic Scenario Loss for Buildings Rank County Direct Economic Loss for Buildings from Scenarios 1 Salt Lake $42,142,226,000 2 Davis $10,034,629,000 3 Utah $9,629,053,000 4 Weber $7,392,349,000 5 Washington $1,146,685,000 6 Box Elder $895,097,000 7 Iron $705,281,000 8 Cache $430,547,000 9 Tooele $255,543, Sevier $158,383, Juab $106,931, Summit $42,518, Wasatch $13,994, Sanpete $9,118, Morgan $8,582, Millard $1,504, Beaver $765, Garfield $753, Carbon $424, Emery $395, Piute $390, Duchesne $220, Rich $201, Kane $95, Uintah $42, Daggett $0 26 Grand $0 26 San Juan $0 26 Wayne $0 Total $72,975,722,000 Page 112

27 Figure 2D-18 Combined Estimated HAZUS Earthquake Scenario Losses by County Page 113

28 Figure 2D-19 Combined Estimated HAZUS Earthquake Scenario Per Capita Losses by County Page 114

29 Table 2D-6 Direct Economic Scenario Loss for Buildings Rank County Direct Economic Per Capita Loss for Buildings from Scenarios 1 Salt Lake $40,928 2 Davis $32,742 3 Weber $31,969 4 Utah $18,641 5 Box Elder $17,911 6 Iron $15,278 7 Juab $10,436 8 Washington $8,302 9 Sevier $7, Tooele $4, Cache $3, Summit $1, Morgan $ Wasatch $ Sanpete $ Piute $ Garfield $ Millard $ Beaver $ Rich $89 21 Emery $36 22 Carbon $20 23 Kane $13 24 Duchesne $12 25 Uintah $1 26 Daggett $0 26 Grand $0 26 San Juan $0 26 Wayne $0 Future HAZUS Scenario Enhancements In addition to re-running the current scenarios using the data enhancements provided by FEMA Region VIII, DEM intends to develop another set of scenarios to further enhance earthquake loss estimates around the state. Currently, DEM is in the process of developing a M 7.3 East Cache Fault scenario, representing a maximum credible event on this fault. DEM obtained the magnitude for this scenario from the HAZUS fault database. Page 115

30 There are currently four segments of the Wasatch Fault that we do not have an existing HAZUS scenario for: Clarkston Segment, Fayette Segment, Levan Segment and the Malad City (Idaho) Segment. Scenario ShakeMaps for these events have been developed by the University of Utah Seismograph Stations, but these will likely need to be recreated because of newer available attenuation functions. These scenarios are: Clarkston Segment -- Wasatch Fault -- M 6.5 Fayette Segment -- Wasatch Fault -- M 6.2 Levan Segment -- Wasatch Fault -- M 6.7 Malad City (Idaho) Segment -- Wasatch Fault -- M 6.5 Finally, DEM intends to develop scenarios for the following faults that are in the current HAZUS fault database: Eastern Bear Lake Fault West Cache Fault Joe s Valley Fault Morgan Fault Sevier / Toroweap Fault Stansbury Fault Development Trend Impacts Around 90% of the population in Utah lives in earthquake hazard zones that are active. The older homes and businesses (pre-1975) are at the most risk to earthquakes because they were built before Utah adopted seismic building codes. Tens of thousands of unreinforced masonry structures are scattered throughout Utah, with a high concentration along the Wasatch Front. The risk for earthquakes is high along the Wasatch Front and this area has seen the greatest growth in the state. Areas with high new growth like in Saratoga Springs, Herriman, and Eagle Mountain will have homes and business built with newer seismic codes to help mitigate the threat of damage from earthquakes. Based on the earthquake analysis displayed in Figure 2D-20, the majority of the highest earthquake vulnerability is in northern Utah. Along down the Wasatch Front and central Utah and then into Piute, Garfield and Iron Counties also show high vulnerability to earthquakes. Ten of the 50 fastest growing cities do not fall within the highest vulnerability categories and 5 of the counties with some of the highest vulnerability do not have any of the fastest growing cities in Utah. Of the top three counties with the highest vulnerability to earthquakes (Cache, Weber and Salt Lake, see Table 2D-10), Salt Lake County had the highest growth rate from with 3.0%, while Weber County had the highest from with 1.9%. As Utah continues to grow, and is currently mitigating against earthquakes threats. Earthquake mitigation continues to be challenging, due in part to the fact that large earthquakes happen infrequently in Utah. Page 116

31 Assessing Vulnerability by State Facilities When assessing the vulnerability of state owned facilities, or all facilities for that matter, an understanding of the building code is of extreme importance. Utah building codes began to address seismic design as early as 1975, although the state did not adopt building codes fully addressing seismic safety until It is a fairly safe assumption that buildings constructed prior to 1975 will not perform in an earthquake as well as those building constructed since An increased understanding of seismic events coupled with advances in building design has greatly increased our ability to design and construct buildings that perform better in earthquakes. Safer buildings are a result of scientific gains in the fields of geoscience and structural engineering being accepted and put in practice through building codes. Thus, buildings constructed today will have a superior performance in an earthquake than those constructed in the past. Earthquakes are regional hazards effecting multi-county areas, and because almost the entire state could experience a seismic event, all of the state owned buildings exhibit some degree of risk. The degree of risk is determined by several factors, none more important than the likelihood and potential magnitude of the earthquake, although when discussing potential building damage regardless of location, building design is a key factor. Vulnerability of state owned facilities was determined through age of construction with those buildings built before 1975 considered having a higher risk. The number of pre-1975 buildings was gathered from the 2012 state facility database. Not all of the facility data in the database indicated a building year. In addition, not all of the data included buildings, but included many different types of assets that the state owns, like sheds. Shown in Table 2D-7 is the number of state buildings in each county built prior to1975 and in Table 2D-8 is the number of people per county for every pre-1975 state owned facility in each county. Page 117

32 Table 2D-7 Number of State Owned Facilities per County Built pre-1975 County Pre-1975 State Facilities Salt Lake 656 Cache 241 Weber 160 Utah 150 Davis 75 Iron 64 Box Elder 53 Carbon 49 Washington 41 Sanpete 39 Uintah 38 Emery 36 Grand 31 Wasatch 31 San Juan 30 Duchesne 26 Garfield 25 Sevier 24 Millard 22 Wayne 22 Morgan 20 Kane 19 Tooele 19 Juab 18 Summit 18 Beaver 14 Daggett 13 Rich 13 Piute 8 Based on Table 2D-9 Page 118

33 Table 2D-8 Population per Pre-1975 State Owned Facility County Pre-1975 State Population per Pre-1975 Owned Facilities State Owned Facility Davis Utah Washington Tooele Summit Salt Lake Weber Box Elder Uintah Sevier Wasatch Duchesne Iron Sanpete Juab Millard San Juan Morgan Cache Beaver Carbon Kane Emery Grand Garfield Piute Rich Wayne Daggett Based on Table 2D-9 and census 2012 estimate data. Estimating Potential Losses by State Facilities To estimate the potential losses a seismic event would cause to state owned facilities, age of construction was considered. This time the construction date of a building was utilized to determine the value or expected damage based on the building s insured value. To determine the value of vulnerable state-owned facilities, the 2012 state-owned building database was queried to identify the number of buildings, age of building construction, and insured value of those buildings for each county. There were a total of 6717 facilities in the end result. The number of facilities is lower than the number of facilities in the Page 119

34 database as a function of the quality of the data. Not every building had a building date and some of the data includes other facilities besides buildings, such as sheds and shacks. The insured value was then used to determine estimated building damage that would result from an event with ground motion of 0.25 and 0.55 PGA. Loss estimation tables from FEMA publication Understanding Your Risk - Identifying Hazards and Estimating Losses were utilized to obtain the percentage of damage expected at the two different PGA values. Rather than determine the building type of all state-owned facilities, the values in Table 2D-9 are for apartment buildings only. This building type seemed most similar to the majority of state-owned facilities. We assumed moderate building code construction for reinforced masonry structures built during and after 1975, and pre-code construction for unreinforced masonry structures built before Damage estimates for structures built before 1975 assume 12.6% damage at 0.25 PGA and 43.7% damage at 0.55 PGA. Damage estimates for structures built since 1975 assume 4.0% damage at 0.25 PGA and 24.5% damage at 0.55 PGA. Content values were not figured into Table 2D-9, as they are most likely included in the insured value. This may have slightly increased the expected damage because as a rule content valued is one half of the expected building damage. For example, building damage for pre-code construction in an unreinforced masonry structure with a ground motion event of 0.55 PGA has an estimated percent damage of Statistical estimates indicate that the contents damage would be 21.85% of the building s replacement value. Table 2D-9 Potential Damage to State Owned Facilities County Name Buildings (Year Built) Count Insured Value Page 120 Expected Building damage at 0.25 PGA (g) Expected Building damage at 0.55 PGA (g) Beaver Pre $17,845,689 $2,248,557 $7,798, $154,904,236 $6,196,169 $38,726,059 Total 41 $172,749,925 $8,444,726 $46,524,625 Box Elder Pre $234,794,271 $29,584,078 $102,605, $154,904,236 $6,196,169 $38,726,059 Total 129 $389,698,507 $35,780,248 $141,331,155 Cache Pre $832,527,493 $104,898,464 $363,814, $803,092,494 $32,123,700 $200,773,124 Total 578 $1,635,619,987 $137,022,164 $564,587,638 Carbon Pre $87,601,173 $11,037,748 $38,281, $128,410,602 $5,136,424 $32,102,651 Total 137 $216,011,775 $16,174,172 $70,384,363 Daggett Pre $7,323,722 $922,789 $3,200, $6,861,373 $274,455 $1,715,343 Total 26 $14,185,095 $1,197,244 $4,915,810 Davis Pre $684,959,501 $86,304,897 $299,327, $1,028,191,985 $41,127,679 $257,047,996

35 Total 286 $1,713,151,486 $127,432,577 $556,375,298 Duchesne Pre $81,014,961 $10,207,885 $35,403, $134,626,389 $5,385,056 $33,656,597 Total 102 $215,641,350 $15,592,941 $69,060,135 Emery Pre $51,670,817 $6,510,523 $22,580, $57,865,867 $2,314,635 $14,466,467 Total 140 $109,536,684 $8,825,158 $37,046,614 Garfield Pre $24,300,240 $3,061,830 $10,619, $33,558,301 $1,342,332 $8,389,575 Total 72 $57,858,541 $4,404,162 $19,008,780 Grand Pre $33,707,649 $4,247,164 $14,730, $48,212,298 $1,928,492 $12,053,075 Total 85 $81,919,947 $6,175,656 $26,783,317 Iron Pre $160,295,214 $20,197,197 $70,049, $401,867,607 $16,074,704 $100,466,902 Total 235 $562,162,821 $36,271,901 $170,515,910 Juab Pre $13,824,853 $1,741,931 $6,041, $60,039,723 $2,401,589 $15,009,931 Total 58 $73,864,576 $4,143,520 $21,051,392 Kane Pre $26,457,408 $3,333,633 $11,561, $14,675,987 $587,039 $3,668,997 Total 64 $41,133,395 $3,920,673 $15,230,884 Millard Pre $35,944,693 $4,529,031 $15,707, $119,823,057 $4,792,922 $29,955,764 Total 78 $155,767,750 $9,321,954 $45,663,595 Morgan Pre $22,757,016 $2,867,384 $9,944, $33,351,075 $1,334,043 $8,337,769 Total 63 $56,108,091 $4,201,427 $18,282,585 Piute Pre $11,344,258 $1,429,377 $4,957, $8,473,098 $338,924 $2,118,275 Total 33 $19,817,356 $1,768,300 $7,075,715 Rich Pre $11,978,569 $1,509,300 $5,234, $11,160,674 $446,427 $2,790,169 Total 67 $23,139,243 $1,955,727 $8,024,803 Salt Lake Pre $3,753,281,850 $472,913,513 $1,640,184, $6,437,198,843 $257,487,954 $1,609,299,711 Total 2230 $10,190,480,693 $730,401,467 $3,249,483,879 San Juan Pre $71,375,764 $8,993,346 $31,191, $101,379,240 $4,055,170 $25,344,810 Total 128 $172,755,004 $13,048,516 $56,536,019 Sanpete Pre $59,107,729 $7,447,574 $25,830, $355,979,642 $14,239,186 $88,994,911 Total 193 $415,087,371 $21,686,760 $114,824,988 Sevier Pre $42,765,151 $5,388,409 $18,688, $163,850,713 $6,554,029 $40,962,678 Total 125 $206,615,864 $11,942,438 $59,651,049 Summit Pre $12,073,024 $1,521,201 $5,275, $272,178,703 $10,887,148 $68,044,676 Page 121

36 Total 130 $284,251,727 $12,408,349 $73,320,587 Tooele Pre $112,841,916 $14,218,081 $49,311, $201,340,128 $8,053,605 $50,335,032 Total 88 $314,182,044 $22,271,687 $99,646,949 Uintah Pre $79,600,276 $10,029,635 $34,785, $234,861,318 $9,394,453 $58,715,330 Total 144 $314,461,594 $19,424,087 $93,500,650 Utah Pre $733,968,171 $92,479,990 $320,744, $2,410,810,709 $96,432,428 $602,702,677 Total 593 $3,144,778,880 $188,912,418 $923,446,768 Wasatch Pre $28,779,100 $3,626,167 $12,576, $169,872,342 $6,794,894 $42,468,086 Total 173 $198,651,442 $10,421,060 $55,044,552 Washington Pre $106,338,179 $13,398,611 $46,469, $748,048,420 $29,921,937 $187,012,105 Total 245 $854,386,599 $43,320,547 $233,481,889 Wayne Pre $12,867,480 $1,621,302 $5,623, $2,493,628 $99,745 $623,407 Total 34 $15,361,108 $1,721,048 $6,246,496 Weber Pre $862,025,551 $108,615,219 $376,705, $1,101,611,573 $44,064,463 $275,402,893 Total 440 $1,963,637,124 $152,679,682 $652,108,059 Damage estimates utilized tables from FEMA 386-2, page The state building database was obtained from the Utah Department of Administrative Services, Division of Risk Management. The insured value of each building is based on the value of each building for the fiscal year (FY) The building database includes K-12 schools as well as facilities for colleges and universities. In Table 2D-10, the damage estimates for pre-1975 and buildings was calculated per state owned facility for every county. This was accomplished by dividing the damage estimates from Table 2D-9 by the number of pre-1975 and buildings for every county. The results show an estimate of the insured value, expected building damage at 0.25 PGA (g), and the expected building damage at 0.55 PGA (g) per facility for every county. The table indicates that the insured value of pre-1975 buildings is for a higher dollar amount for all of the counties except, Beaver, Juab, Millard, Sanpete, Summit, Uintah, Utah, Wasatch, and Washington. Also, the expected building damage estimates at both 0.25 PGA (g) and 0.55 PGA (g) are higher for the pre-1975 buildings for every county in Utah except for Beaver and Summit. Table 2D-10 highlights the vulnerability and high damage costs associated with pre-code 1975 state owned facilities. Page 122

37 Table 2D-10 Potential Damage per State Owned Facility County Buildings (Year Built) Count Insured Value (per facility) Page 123 Expected Building damage at 0.25 PGA (g) (per facility) Expected Building damage at 0.55 PGA (g) (per facility) Beaver Pre $1,274, $160, $557, $5,737, $229, $1,434, Box Elder Pre $4,430, $558, $1,935, $2,038, $81, $509, Cache Pre $3,454, $435, $1,509, $2,383, $95, $595, Carbon Pre $1,787, $225, $781, $1,459, $58, $364, Daggett Pre $563, $70, $246, $527, $21, $131, Davis Pre $9,132, $1,150, $3,991, $4,872, $194, $1,218, Duchesne Pre $3,115, $392, $1,361, $1,771, $70, $442, Emery Pre $1,435, $180, $627, $556, $22, $139, Garfield Pre $972, $122, $424, $714, $28, $178, Grand Pre $1,087, $137, $475, $892, $35, $223, Iron Pre $2,504, $315, $1,094, $2,350, $94, $587, Juab Pre $768, $96, $335, $1,500, $60, $375, Kane Pre $1,392, $175, $608, $326, $13, $81, Millard Pre $1,633, $205, $713, $2,139, $85, $534, Morgan Pre $1,137, $143, $497, $775, $31, $193, Piute Pre $1,418, $178, $619, $338, $13, $84, Rich Pre $921, $116, $402, $206, $8, $51, Salt Lake Pre $5,721, $720, $2,500, $4,089, $163, $1,022, San Juan Pre $2,379, $299, $1,039,706.97

38 $1,034, $41, $258, Sanpete Pre $1,515, $190, $662, $2,311, $92, $577, Sevier Pre $1,781, $224, $778, $1,622, $64, $405, Summit Pre $670, $84, $293, $2,430, $97, $607, Tooele Pre $5,939, $748, $2,595, $2,917, $116, $729, Uintah Pre $2,094, $263, $915, $2,215, $88, $553, Utah Pre $4,893, $616, $2,138, $5,442, $217, $1,360, Wasatch Pre $928, $116, $405, $1,196, $47, $299, Washington Pre $2,593, $326, $1,133, $3,666, $146, $916, Wayne Pre $584, $73, $255, $207, $8, $51, Weber Pre $5,387, $678, $2,354, $3,934, $157, $983, An analysis of taking the expected damage at 0.55 PGA (g) for pre-1975 buildings (from Table 2D-9) in every county and ranking the damage estimates from most damage to least damage for all of the 29 counties reveals that the top five counties with the highest estimated damage are Salt Lake, Weber, Cache, Utah and Davis Counties in that order. These counties lie along the Wasatch Front and consist of 5 of the 6 most populous counties in Utah in Doing the same analysis for the expected damage at 0.55 PGA (g) per facility from Table 2D-10 for every county reveals some minor changes. The top five counties with the most damage amount at 0.55 PGA (g) per facility are Davis, Tooele, Salt Lake, Weber, and Utah. Tooele jumped from being eighth in the total estimated damage for all facilities to being second for estimated damage based on per facility damage. Another change to note is that the mostly rural Piute County went up ten places from twenty-eighth to eighteenth place. Table 2D-11 is comprised of the per capita state owned facility loss based on the insured value of the pre-1975 facilities as contained in Table 2D-9. The table ranks the per capita insured value loss of pre-1975 buildings from highest loss to least. Table 2D-11 highlights the impact earthquake damage would have state facilities in Utah s rural counties. Piute County, Daggett County, and Rich County were ranked 1, 3 and 4 respectively and are also the three least populated counties in Utah. Salt Lake County, the most populated county is down in fifteenth place. The majority of the populated counties are on the bottom of the table. Page 124

39 Table 2D-11 Pre-1975 Per Capita Loss for State Owned Facilities (from Table 2D-9) Vulnerability Analysis Rank County Pre-1975 State Owned Facilities Per Capita Loss 1 Piute $7, Cache $7, Daggett $6, Rich $5, San Juan $4, Garfield $4, Emery $4, Wayne $4, Box Elder $4, Duchesne $4, Carbon $4, Kane $3, Weber $3, Grand $3, Salt Lake $3, Iron $3, Millard $2, Beaver $2, Morgan $2, Uintah $2, Davis $2, Sanpete $2, Sevier $2, Tooele $1, Utah $1, Juab $1, Wasatch $1, Washington $ Summit $ A vulnerability analysis was performed based on 5 criteria contained in Tables 2D-3, 4, 7, 8, and 11. These criteria include the HAZUS total direct economic losses for buildings (Table 2D-3), the per capita loss estimates from HAZUS (Table 2D-4), the number of state owned facilities per county (Table 2D-7), the county population per pre-1975 state owned facility (Table 2D-8), and the county per capita loss for state owned facilities (Table 2D-11). Each of the criteria was ranked from 1 to 29 for each county (see Table 2D-11 as an example). The ranking numbers Page 125

40 were combined for each county and then the totals were ranked from 1 to 29 to determine a vulnerability ranking. Because some counties had the same vulnerability score they received the same ranking number. The counties with the lowest total ranking number would indicate the highest overall vulnerability to earthquakes. For example, if a county ranked 1 for each of the criteria it would receive a vulnerability ranking of 5 and be scored as having the highest vulnerability to earthquakes. Table 2D-12 and Figure 2D-20 list the results of the analysis. This analysis does not represent the likelihood of earthquakes impacting a county, but the vulnerability of a county to earthquakes based on the 5 criteria. Table 2D-12 Earthquake Vulnerability of Utah Counties* Rank County Vulnerability Score 1 Cache 27 2 Salt Lake 42 3 Weber 45 4 Box Elder 49 5 Rich 53 6 Garfield 54 7 Davis 61 7 Piute 61 8 Carbon 62 9 Iron Utah Emery Sanpete Beaver Daggett Wasatch Wayne Millard Kane Sevier Duchesne Grand Juab San Juan Tooele Washington Uintah Morgan Summit 105 *Based on 5 criteria from earthquake risk assessment. Page 126

41 Figure 2D-20 Earthquake Vulnerability of Utah Counties with 50 Fastest Growing Cities from The results of Table 2D-12 and Figure 2D-20 show that the majority of the vulnerability to earthquakes in Utah based on the five criteria is located in northern Utah and along the Wasatch Front. Cache County came in as the most vulnerable county, followed by Salt Lake and Weber Counties. Rich and Garfield Counties were ranked as number 5 and 6. These two counties are also two of the least populated counties in the state. This indicates that not just the populated counties are highly vulnerable to earthquakes. As discussed above in the Development Trends Impact section, the majority of Utah s 50 fastest growing lie within the most vulnerable counties. Summit and Morgan Counties were found to be the least vulnerable. Page 127

42 Local Jurisdiction Vulnerability and Loss Estimates Earthquakes A map was created to show the hazard ranking of the landslide hazard for each county as reported in the LHMPs (Figure 2F-2). The hazard ranking is calculated from a combination of severity (categorized from 0-3) and frequency (categorized from0-3). This ranking is located in the LHMPs. The SHMPC added all of the counties rankings from their plans, for a ranking from 0-6 to be scored. The map highlights the highest at risk counties (a rank 5) whose population growth rates are 1.5% (the state average) or greater. This is designed to mark areas of rapid growth and development by county that are the highest risk to earthquakes as reported in LHMPs. Figure 2D-21 Earthquake Hazard Rankings from LHMPs Page 128

43 Figure 2D-21 illustrates that based on LHMP reporting Salt Lake, Davis, Morgan, Weber, and Tooele counties (all of which comprise the Wasatch Front Regional Council) perceive themselves as the highest vulnerability to earthquakes. Salt Lake, Davis, Morgan, and Weber counties have also had great growth from The lowest vulnerability rankings are in the southwestern corner of the state and northeastern corner. Local jurisdictions also produce loss estimations for an earthquake event. Earthquake loss estimates are typically derived on a countywide basis. Some counties elect to produce loss estimates for each jurisdiction in the county, while others only report loss estimates for the entire county. These loss estimates gives the SHMPC a better understanding of the amount of damage that could be expected after an earthquake and helps us prioritize our mitigation efforts. These are included for reference. Beaver County This table is taken from page 6-21 of the 2010 Five County AOG hazard mitigation plan. Five County AOG is in the process of updating a new mitigation plan. Box Elder County Earthquake loss estimations shown here reflect values taken from the November 2009 Pre- Disaster Mitigation Plan produced by BRAG. BRAG is in the process of updating a new mitigation plan. The following tables are taken from pages of the BRAG plan. Page 129

44 Page 130 Earthquakes

45 Page 131 Earthquakes

46 Cache County Earthquake loss estimations shown here reflect values taken from the November 2009 Pre- Disaster Mitigation Plan produced by BRAG. BRAG is in the process of updating a new mitigation plan. The following tables are taken from pages of the BRAG plan. Page 132

47 Page 133 Earthquakes

48 Page 134 Earthquakes

49 Garfield County This table is taken form page 7-23 of the 2010 Five County AOG hazard mitigation plan. Iron County This table is taken form page 8-25 of the 2010 Five County AOG hazard mitigation plan. Kane County This table is taken form page 9-28 of the 2010 Five County AOG hazard mitigation plan. Salt Lake County Salt Lake County is in the process of updating a new mitigation plan. Page 135

50 Summit County This table comes from page 24 of Part VI of the 2010 Mountainland Mitigation Plan. Residential Commercial Hazard Count Cost Count Cost Earthquake 69 $23,479, $ 5,328, Davis County Davis County is in the process of updating a new mitigation plan. Utah County This table comes from page 66 of Part VII of the 2010 Mountainland Mitigation Plan Residential Commercial Bridges Critical Facilities Length Count Cost Count Cost Cost Count Hazard (mi) Earthquake 58,449 $9,445,163, $1,506,695, $1,818,707, Page 136

51 Wasatch County This table comes from page 117 of Part VIII of the 2010 Mountainland Mitigation Plan. Residential Commercial Hazard Count Cost Count Cost Earthquake 256 $27,876, $6,996, Washington County This table is taken form page of the 2010 Five County AOG hazard mitigation plan. Weber County Weber County is in the process of updating a new mitigation plan. Page 137