New data arrived in June!

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1 New data from the Val-des-Bois, Québec, Earthquake of June 23, 2010 John Adams and Lan Lin Geological Survey of Canada, Natural Resources Canada, Ottawa, Ontario K1A 0Y Copyright. Her Majesty the Queen in Right of Canada, 2010 New data arrived in June! Context of the earthquake and its effects Released records Early impact on eastern GMPEs Unreleased records considerable work has to go into accessing the records and documenting their context before they should be used (we can process the records faster than we can understand them ) Val-des-Bois, Québec, Earthquake of June 23, :41 pm EDT June 23 rd 2010 Magnitude (Mw) km NNE of Ottawa Earthquake notifications sent to critical infrastructure operators within 6 minutes Largest aftershock happened at T +6 hours, mn=3.3 Total felt area (potentially felt by about 19 million people) Web reports from 59,000 people to Did You Feel It? Felt much farther to the southwest than to the northeast Only weakly felt into eastern Quebec The bottom line Bad news: Strongest shaking in Ottawa s history Good News: Much weaker than the current earthquake designs 1

2 Details of felt intensity Intensity varies with soil conditions strongest on thick clay Geocoding of postal codes allows assignment to city blocks Hope to match to and test soil amplification maps of Ottawa prepared by GSC & Carleton Univ; e.g. Pal and Atkinson (submitted BSSA) Ottawa soil amplification map Earthquake history in Ottawa ~5% Val-des-Bois* ~2% Thurso Feb 2006 ** GSC s Val-des-Bois web intensity values (Halchuk: CHIS report ) * More on soft soil ** Less in the west-end Why do earthquakes happen here? Failed Rift Structural trends parallel to focal mechanism planes Failed Rift Ancient Rifted margin Hot Spot Focal mechanism by R Herrmann June 23, :01 Mw = 5.04 Z = 22 km Plane Strike Dip Rak NP NP

3 How often do earthquakes happen near Ottawa? June 23 rd shaking in Ottawa was about once-per-150-year level shaking Magnituderecurrence for earthquakes within 250 km of Ottawa. June 23 rd was Mw=5.0 (mn=5.6) Rate about once per years 0.6 M>4 events p.a. Val-des-Bois earthquake - Aftershocks mainshock NRCan seismometer at Mont-Tremblant (TRQ) captured the main shock and all the aftershocks screen capture Wednesday 23 rd at 1833EDT 11 aftershocks above magnitude < 2.5 in first 2 hours Largest aftershock so far at T+6 hours, magnitude located to date, less than a dozen reported felt NRCan is continuing to locate aftershocks using permanent network Field seismographs deployed for the first few weeks will help refine the map distribution 3

4 Aftershocks the first 24 hours Examples of June 23 rd earthquake effects Field recorders were installed near the earthquakes to refine aftershock locations and depth Val-des-Bois VDBQ Lac Echo Workers unsure what to do.. Continuous strong motion from VDBQ from T+26 hours Data to date uninteresting Lac de l Argile 5 km Blair Business Park was evacuated after an earthquake tremor in Gloucester, near Ottawa. (Submitted by Rohit Saxena) Pictures of Sign Out Sheet at John Young School, Kanata. Grade 6 Graduation ceremonies at John Young were interrupted by the earthquake. Reason for sign out... EARTHQUAKE Photograph by: Laura Kelland-May, news/earthquake/reader +Gallery+Ottawa +Earthquake/ / story.html#ixzz0rtk2n3jr Val-des-Bois Minor damage to chimneys and contents Hazard for bare feet! New safety instructions at Ottawa Catholic school board Do not exit a building during an earthquake Evacuate only if there are signs of structural damage, fire/ smoke, gas leaks or other life-threatening situations Avoid use of cell phones 4

5 Ottawa Citizen Nov 14th Earthquake spilled toxic mercury The June 23 quake, measured at 5.0 on the Richter scale, rocked the historic lighthouse on the museum's front lawn, causing a part of a pool of mercury to spill out of its bowl. Mercury was sometimes used in lighthouses built after 1890 to float the main light mechanism, allowing the heavy structure to rotate with virtually no friction. The main cleanup was completed by July 20, costing the poorly funded museum $7,000 Barbara Ann Scott Arena in Ottawa is closed so workers can remove bricks loosened by the quake, which could fall. (Simon Gardner/CBC) At least 30 Ottawa schools were damaged, 4 had possible structural problems. Several other municipal buildings are also damaged, including one fire station near the Barbara Ann Scott Arena Landslides Embankment failure south of Bowman 11 km 17 km Embankment failure south of Bowman, Quebec. Photograph by: Jean Levac, The Ottawa Citizen. 5

6 Landslides Chemin Binette 11 km from epicentre Happened the next day 400 m Greg Brooks photomosaic Strong motion records Preliminary reports available via web at EarthquakesCanada.ca 47 hours after the earthquake Stations with records from the Val-des-Bois earthquake recovered within 47 hours (Etna instruments had to be visited) 6

7 Ottawa (Orleans) strong motion record (Adams house) about 7%g on soil Foundation of OT002 2-storey wood frame house on ~30 m clay in Orleans, constructed 1986 Ottawa records from Class C instruments Rock Internet Accelerometer installation Montreal records Montreal ~0.5%g Ottawa 3-8%g 7

8 Weak Motion Records Seismological Research Letters v81(5) Sept/Oct 2010 GSC report on nearby stations T=1s T=0.1s Gail Atkinson has added the GSC data to her seismo toolbox and applied it in recent papers Other Records not yet released Bedrock seismograph LSQ1 3-cpt record on hard, hard rock at seismologist s cottage, distance 53 km AB06 AB06 with higher stress parameter than before was 140 bars in AB06, now 240 at Mw 5 sliding down to 70 at Mw=8 8

9 Potential records from Nanometrics in Kanata Seismometer testing facilities Some records on rock, some on soil (site conditions to be verified) Seismometer and accelerograph records Distances ~70 km Records not yet supplied by Nanometrics Parliament Hill Ottawa Three major towers, all load-bearing masonry construction Instrumented with Etna and SSA2 at multiple levels Peace Tower of the Centre Block 1927 h=92 m Mackenzie Tower of the West Block 1878 h=81m South-West Tower of the East Block 1866 h=? Soil condition : in structures on bedrock Records being processed with staff from PWGSC Peace Tower Mackenzie Tower Parliament Hill - representative ground level record Level E (3 cpt) Level B (4 cpt) Level 8 (2 cpt) Top floor (3 cpt) Level 4 (3 cpt) Representative PGA values (g) Ground Level (3 cpt) Ground Level (3 cpts) Tower At base At top Peace NS 0.49 NS Mackenzie EW EW South-west NS 0.19 EW 9

10 Parliament Hill - FFT analysis Mackenzie Tower Dominant period of the vibration in NS direction: 0.61 s Important: consistent with the result from ambient test 0.56 s.ground records may be contaminated by structure and/or SSI Records from Gaz Metro Montreal * Distance about 150 km 3 component record Maximum PGA: 1.5%g Free-field site, away from LNG tanks Soil condition: rock (possibly <2 m interveaning clay) Important for interpreting the 4 Montreal soil records Records from Gaz Metro (cont.) NS component: PGA=1.5%g Records from Gaz Metro (cont.) Comparison with records from Napierville Eq. VDB Eq, Mw=5.0 Napierville Eq, Mw=4.3 EW component: PGA=1.4%g V component: PGA=0.3%g Similar shapes and relative amplitudes of the waveforms (VDB amplitude is twice that for Napierville) 10

11 Record from Hydro-Quebec Distance about 70 km PGA ~4%g Soil, greater than 23 m thickness Record from deep soil site Ottawa John Shaw Road about 76 km dist broadband sensor thick soil Clipped! Record from ambient noise soil survey, Gatineau Distance about 50 km Broadband Tromino sensor thick soil Clipped! June 23 rd shaking in Ottawa was about once-per-150-year level of shaking only 1/5 th as strong as current building code requires Excellent data set for Mw=5.0 Earthquake design shaking in Ottawa on rock Shaking recorded at OTT on rock compared with the design spectra for rock and soil at Ottawa, according to National Building Code of Canada 2005 Val-des-Bois earthquake shaking on rock 11