Tsunami Hazard Map of the Warrenton Area, Clatsop County, Oregon

Transcription

1 CEDAR Lewis STATE OF OREGON DEPARTMENT OF GEOLOGY AND MINERAL INDUSTRIES DONALD A. HULL, STATE GEOLOGIST 124 Tsunami Hazard Map of the Warrenton Area, Clatsop County, Oregon 1999 MAP EXPLANATION (see accompanying text for complete map explanation) IMS-12 Tsunami Hazard Map of the Warrenton Area, Clatsop County, Oregon By G.R. Priest and others Funded by Federal Emergency Management Agency Cooperative Agreement Number EMS-97-CA-0058 (from funds originally given to the National Oceanic and Atmospheric Administration for tsunami hazard mitigation) and the Oregon Department of Geology and Mineral Industries Extreme risk zone for tsunami flooding ( year events) Clatsop High risk zone for tsunami flooding ( year events) Spit Moderate risk zone for tsunami flooding ( year events) Point Adams Columbia Low to negligible risk zone for tsunami flooding ( year events) Clatsop Spit Jetty Jetty Sands Lagoon FORT STEVENS MUSEUM River How to use the Map: Mapped boundaries may be viewed as guides for evacuation planning in the event of an earthquake and tsunami. If an earthquake occurs with 20 seconds or more of shaking that is strong enough to make standing difficult, plan on going immediately to the lowest risk site available. A tsunami could arrive within a few minutes of the earthquake. Such nearby earthquakes and associated tsunamis only occur on the order of years. Distant tsunamis (teletsunamis) occur more often, are generally smaller than tsunamis from nearby earthquakes, and arrive hours after a distant earthquake. The West Coast and Alaska Tsunami Warning Center issues warnings for all teletsunamis affecting the west coast of the United States. Map prepared by: George R. Priest, Oregon Department of Geology and Mineral Industries, from numerical simulations of Edward Myers and Antonio Baptista, Oregon Graduate Institute of Science & Technology, and Robert A. Kamphaus, Center for Tsunami Inundation Mapping Effort, National Oceanic and Atmospheric Administration. All of these individuals are co-authors on this map and should be listed in order indicated for bibliographic citations ' 30" COLUMBIA RIVER VIEWPOINT RUSSELL BATTERY RUSSELL BURMA Swash TYEE 3RD 3RD SILVERSIDE RUSSELL SILVERSIDE PACIFIC QUINNAT 7TH PEACOCK 2ND MARINER U.S. ARMY FORT STEVENS CEMETERY LAKE LAKE 3RD 4TH 5TH KING SALMON 9TH KING SALMON 12TH Hammond BOAT Marina RAMP PACIFIC FIRE STA. IREDALE HECETA 7TH 8TH FORMER PT. ADAMS COAST GUARD STATION HECETA 7TH 5TH FORT PACIFIC GRAY FLEET ENTERPRISE STEVENS 8TH CHINOOK DESDEMONA 10TH 12TH CITY PARK EBEN CARRUTHERS MEMORIAL PARK 14TH Tansy Point DISCLAIMER The Oregon Department of Geology and Mineral Industries is publishing this map because the subject matter is consistent with the mission of the Department. The map is not intended to be used for site specific planning. It may be used as a general guide for emergency response planning. 13TH Tansy Cr. 11TH NO. 104 Pacific PETER IREDALE RIDGE 9TH 7TH WATERWAY Youngs Alder Coffenbury DATE CEDAR Ponds Ocean Columbia Beach DELAURA GIRLSCOUT CAMP KIWANILONG CAMP 14TH PINE BEACH Pond 14TH Lily LANDFILL JUNIPER JUNIPER GARDENIA HARBOR OCEAN VIEW CEMETERY OCEAN VIEW Smith HARBOR Burke DUMP DELAURA BEACH ELM 2ND CEDAR CEMETERY DATE 7TH 9TH LP. CEDAR BIRCH 3RD CITY PARK CEDAR 10TH 11TH FORT STEVENS BIRCH 7TH ALDER MAIN MAIN 8TH 4TH HARBOR ALDER 4TH 5TH ELEM. SCHOOL NO. 104 NAIN 13TH ANCHOR ANCHOR 15TH F.S. 13TH MAIN 14TH FORT RIVER SKIPANON HIGH SCHOOL 5TH 2ND HARBOR ANCHOR HARBOR STEVENS SKIPANON BAY ENSIGN 7TH Mooring Basin HARBOR 14TH COAST Skipanon GALENA 14TH HERON SPUR SKIPANON KING - 13TH 13TH SUBSTATION HARBOR KING HARBOR 2ND ASTORIA 5TH MARLIN 7TH 9TH 10TH NEPTUNE 12TH Holbrook Adair Vera AIRPORT CLATSOP Bay U.S. COAST GUARD AIR STATION PORT OF ASTORIA AIRPORT AIRPORT FLIGHT LINE OREGON 46 10' Fork FORT - - ASTORIA COLUMBIA BEACH WHISKEY COLUMBIA Neacoxie LAKE STEVENS X DOLPHIN HANSEN BEACH OREGON CRANBERRYACRES Old Skipanon CLATSOP Clark River 46 08' Green and PERKINS RAILROAD DOLPHIN ' 30" Base map modified from Oregon Department of Transportation, City Map Series, Warrenton digital file Universal Transverse Mercator projection NAD 1927, NAVD 29 Public Land Survey System shown with red ticks and associated section numbers O R E G O N Scale 1:24, Mile This map is available from: The Nature of the Northwest Information Center 800 NE Oregon Street #5 Portland, OR / and the Baker City and Grants Pass, Oregon field offices of the Oregon Department of Geology and Mineral Industries Location Map

2 State of Oregon Department of Geology and Mineral Industries John D. Beaulieu, State Geologist IMS-12 Tsunami Hazard Map of the Warrenton Area, Clatsop County, Oregon By G.R. Priest and others Text How to Use the Map Mapped boundaries may be viewed as guides for evacuation planning in the event of an earthquake and tsunami. If an earthquake occurs with 20 seconds or more of shaking that is strong enough to make standing difficult, plan on going immediately to the lowest risk site available. A tsunami could arrive within a few minutes of the earthquake. Such nearby earthquakes and associated tsunamis occur in intervals of approximately years. Distant tsunamis (teletsunamis) occur more often, are generally smaller than tsunamis from nearby earthquakes, and arrive hours after a distant earthquake. The West Coast and Alaska Tsunami Warning Center issues warnings for all teletsunamis affecting the West Coast of the United States. Map Hazard Categories White Yellow Low to negligible risk zone for tsunami flooding (300- to 600- year events) Moderate risk zone for tsunami flooding (300- to 600-year events) Elevations within and below this zone would be flooded by a Cascadia subduction zone tsunami from a magnitude 9.1 earthquake with doubling of the fault slip immediately offshore. See Model 1A Asperity in Priest and others (1997) for a complete explanation of this model earthquake and tsunami. Orange High risk zone for tsunami flooding (300- to 600-year events) Elevations within and below this zone would be flooded by a Cascadia subduction zone tsunami from a magnitude 9.1 earthquake. See Model 1A in Priest and others (1997) for a complete explanation of this model earthquake and tsunami. Red Extreme risk zone for tsunami flooding (300- to 600-year events) Elevations within and below this zone would be flooded by a Cascadia subduction zone tsunami from a magnitude 8.6 earthquake. See Model 2Cn in Priest and others (1997) for a complete explanation of this model earthquake and tsunami. 1

3 The following figures illustrate timing of waves as they arrive after a large earthquake on the nearby Cascadia subduction zone fault system. Figures 1 and 2 illustrate the sequence of water elevation changes from tsunamis arriving after a subduction zone earthquake. See Model 1A in Priest and others (1997) for a complete explanation of this model earthquake and tsunami. Figure 3 shows the expected changes in current direction and speed in the shipping channel for the worst-case scenario tsunami. See Model 1A, Asperity in Priest and others (1997), for a complete explanation of this model earthquake and tsunami. Figure 1. Time history of wave arrivals at Astoria after a magnitude 9.1 earthquake on the nearby Cascadia subduction zone fault system. Negative wave elevations correspond to surges of water heading seaward; positive elevations correspond to surges up the estuary channels. Observation point is immediately offshore from the Hammond boat basin. Note that the first major surge of flooding does not strike this area until about 45 minutes after the earthquake; however, expect some flooding immediately after the earthquake in response to 3 6 ft of local subsidence of the land. Current direction in the estuary channels could be either seaward or landward during the first 30 minutes after the earthquake, depending on how the fault rupture process occurs. Actual tsunami wave elevation at shoreline sites will be higher than shown on the diagram. This illustration should be used to understand approximate timing and relative wave elevation, not absolute wave elevation at the shoreline. It is based on a moderately high tsunami run-up scenario (Model 1A in Priest and others, 1997). 2

4 Figure 2. Time history for same tsunami scenario as in Figure 1 but for wave arrival in Youngs Bay at the Highway 101 bridge. Negative wave elevations correspond to surges of water heading seaward; positive elevations correspond to surges up the estuary channels. Observation point is immediately offshore from the main docks north of the Columbia River bridge. Note that the first major surge of flooding does not strike this area until about 1 hour after the earthquake; however, expect some flooding immediately after the earthquake in response to 3 6 ft of local subsidence of the land. Current direction in the estuary channels could be either seaward or landward during the first 30 minutes after the earthquake, depending on how the fault rupture process occurs. Actual tsunami wave elevation at shoreline sites will be higher than shown in the diagram. This illustration should be used to understand approximate timing and relative wave elevation, not absolute wave elevation at the shoreline. 3

5 4 Figure 3. Estimated tsunami-induced velocities from one hypothetical case; it does not characterize the tsunami-related currents from all possible tsunamis. Tsunami-induced velocities of at least 3 8 knots above and beyond normal tidal and river-induced velocities should be considered in preparing for the impact of a Cascadia subduction zone earthquake in the estuary. Tsunami-induced high velocities may persist for several hours, with sharp changes in direction. Maximum velocities, persistence, and timing of changes in current direction will depend dramatically on the earthquake that generated the tsunami and the tidal and river conditions.

6 When planning evacuation routes and destinations, check with local officials for guidance. In general, one should go to the least hazardous site (noncolored area or the coolest color on the map) by the shortest route, making sure that the route is not compromised by other earthquake hazards such as liquefaction or earthquake-induced landslides. Bridges may fail in the event of an earthquake. Consult with transportation authorities about the seismic stability of bridges used for evacuation. Additional Detailed Information See Oregon Department of Geology and Mineral Industries Open-File Report O (Priest and others, 1997) for a detailed explanation of the mapping techniques. Funding Source Funds for the project were primarily from Federal Emergency Management Agency Cooperative Agreement Number EMS 97 CA 0058 from funds originally given to the National Oceanic and Atmospheric Administration for tsunami hazard mitigation. Funds were also provided by the Oregon Department of Geology and Mineral Industries. Reference Cited Priest, G.R., Myers, E., Baptista, A., Fleuck, P., Wang, K., Kamphaus R.A., and Peterson, C.D., 1997, Cascadia subduction zone tsunamis: Hazard mapping at Yaquina Bay, Oregon: Oregon Department of Geology and Mineral Industries Open-File Report O 97 34, 144 p. Note The Oregon Department of Geology and Mineral Industries is publishing this map because the information furthers the mission of the Department. The map is not intended to be used for sitespecific planning. It may be used as a general guide for emergency-response planning. 5