Predicting Earthquake Shaking and hazard John N. Louie, Nevada Seismological Lab. with UNR...
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Predicting Earthquake Shaking and hazard John N. Louie, Nevada Seismological Lab. with UNR undergraduate interns: Will Savran, Brady Flinchum, Colton Dudley,
Predicting Earthquake Shaking and hazard John N. Louie, Nevada
Seismological Lab. with UNR undergraduate interns: Will Savran,
Brady Flinchum, Colton Dudley, Nick Prina and Geology B.S. graduate
Janice Kukuk J. Louie, NMSLC 3/3/2011
Slide 2
Last Weeks Earthquake in Christchurch, New Zealand Magnitude
6.3 aftershock of M 7.1 in Sept. J. Louie, NMSLC 3/3/2011
Slide 3
Unexpectedly Intense Ground Shaking Horizontal accelerations
>2 times gravity J. Louie, NMSLC 3/3/2011
Slide 4
What Happens with Such Intense Shaking? >200 deaths, 1/3 of
citys buildings destroyed J. Louie, NMSLC 3/3/2011 Stuff.co.nz
Slide 5
Photos by Marilyn Newton, Reno Gazette-Journal Could It Happen
Here? It Already Did! Wells, Nevada, Feb. 2008
Slide 6
How Do We Protect Nevadas People and Economy from Earthquakes?
Stiffen building codes to strengthen buildings everywhere? But,
would make construction too costly But, would make construction too
costly Improve our understanding of earthquake shaking What areas
have high hazard? Put resources there. What areas have high hazard?
Put resources there. Dont waste money reinforcing safer areas Dont
waste money reinforcing safer areas J. Louie, NMSLC 3/3/2011
Slide 7
Three Elements to Predicting Shaking (1) Where are the
earthquake sources? Discover and locate faults with seismic
monitoring and surveying Discover and locate faults with seismic
monitoring and surveying Characterize faults with geology and
seismic surveying Characterize faults with geology and seismic
surveying (2) How will the waves propagate from the sources?
Characterize basins with gravity and seismic surveying Characterize
basins with gravity and seismic surveying (3) How will the soils
under your property react? Seismic microzonation with Parcel
Mapping Seismic microzonation with Parcel Mapping Scenario
predictions with Next-Level ShakeZoning Use physics and geology to
get realistic shaking predictions for likely earthquakes Use
physics and geology to get realistic shaking predictions for likely
earthquakes Combine predictions with probability of each earthquake
Combine predictions with probability of each earthquake Nevada
researchers are working on these challenges. J. Louie, NMSLC
3/3/2011
Slide 8
Adding Fault Geology Black Hills Fault in Google Earth with
USGS Qfaults trace J. Louie, NMSLC 3/3/2011
Slide 9
Adding Geology & Geotechnical Data Black Hills Fault in
Google Earth with USGS Qfaults trace Earthquake Magnitude from
Fault Size M 0 = Ad = 3x10 11 dyne/cm 2 A = Fault Area (cm 2 ) = (9
km length)(10 5 cm/km) (9 km width)(10 5 cm/km) d = fault
displacement = 200 cm (from geologists) J. Louie, NMSLC
3/3/2011
Slide 10
Adding Geotechnical Data ShakeZoning Geotech Map Obtained by
Clark Co. and City of Henderson 10,721 site measurements J. Louie,
NMSLC 3/3/2011
Slide 11
Adding Physics 2 nd -order PDE controls P(x,y,z) waves
evolution in time Uses Laplacian to get spatial derivatives Use
definition of derivative to compute a Finite Difference (dont take
limit) J. Louie, NMSLC 3/3/2011
Slide 12
Wave Computation on a 3D Geological Grid Fine grid gives
accurate FD estimate of derivatives Finer grid takes longer to
compute, higher cost Finer grid for higher shaking frequencies J.
Louie, NMSLC 3/3/2011
Slide 13
Adding Physics Black Hills M6.5 event Short trace but 4-m
scarps noted Short trace but 4-m scarps noted Viscoelastic finite-
difference solution 0.5-Hz frequency 0.5-Hz frequency 0.20-km grid
spacing 0.20-km grid spacing A few hours on our small cluster A few
hours on our small cluster Map view of waves Mode conversion,
rupture directivity, reverberation, trapping in basins J. Louie,
NMSLC 3/3/2011
Slide 14
Showing 3-D Vector Motions 3 computed components of the ground
particle velocity vector: (x, y, z) (x, y, z) 3 components of color
on your computer screen: (R, G, B) (R, G, B) red, green, blue red,
green, blue J. Louie, NMSLC 3/3/2011
Slide 15
Showing 3-D Vector Motions 3 computed components of the ground
particle velocity vector: (x, y, z) (x, y, z) 3 components of color
on your computer screen: (R, G, B) (R, G, B) red, green, blue red,
green, blue J. Louie, NMSLC 3/3/2011 from MathWorks.com
Slide 16
Showing 3-D Vector Motions 3 computed components of the ground
particle velocity vector: (x, y, z) (x, y, z) 3 components of color
on your computer screen: (R, G, B) (R, G, B) red, green, blue red,
green, blue J. Louie, NMSLC 3/3/2011
Slide 17
Showing 3-D Vector Motions 3 computed components of the ground
particle velocity vector: (x, y, z) (x, y, z) 3 components of color
on your computer screen: (R, G, B) (R, G, B) red, green, blue red,
green, blue J. Louie, NMSLC 3/3/2011
Slide 18
Showing 3-D Vector Motions 3 computed components of the ground
particle velocity vector: (x, y, z) (x, y, z) 3 components of color
on your computer screen: (R, G, B) (R, G, B) red, green, blue red,
green, blue J. Louie, NMSLC 3/3/2011
Slide 19
Showing 3-D Vector Motions Add the color components to get a
perceived color Color depends on strength and direction of wave
vibration J. Louie, NMSLC 3/3/2011
Slide 20
Adding Physics Cue up and play: BH-ClarkCo-0.5Hz.m4v Timelapse
animation 60 seconds wave propagation compressed to 16.6 sec video
60 seconds wave propagation compressed to 16.6 sec video Time
compression factor of 3.6 Time compression factor of 3.6 J. Louie,
NMSLC 3/3/2011
Slide 21
Adding Physics Cue up and play: BH-ClarkCo-0.5Hz.m4v 0 seconds
after rupture begins on the Black Hills fault (9 km down) Las Vegas
basin in shaded relief LV H H FM BH J. Louie, NMSLC 3/3/2011
Slide 22
Adding Physics Cue up and play: BH-ClarkCo-0.5Hz.m4v 2.2
seconds after rupture begins on the Black Hills fault Seismic waves
reach the surface in Eldorado Valley LV H H FM BH J. Louie, NMSLC
3/3/2011
Slide 23
Adding Physics Cue up and play: BH-ClarkCo-0.5Hz.m4v 6.9
seconds after rupture begins on the Black Hills fault P wave in Las
Vegas, small (dark yellow) P wave in Las Vegas, small (dark yellow)
Intense surface waves funneling into Henderson Intense surface
waves funneling into Henderson LV H H FM BH J. Louie, NMSLC
3/3/2011
Slide 24
Adding Physics Cue up and play: BH-ClarkCo-0.5Hz.m4v 13.4
seconds after rupture begins on the Black Hills fault Rayleigh wave
in W. Las Vegas, large (red- blue) Rayleigh wave in W. Las Vegas,
large (red- blue) Like ocean wave: vertical in between radial
motions Like ocean wave: vertical in between radial motions LV H H
FM BH J. Louie, NMSLC 3/3/2011
Slide 25
Adding Physics Cue up and play: BH-ClarkCo-0.5Hz.m4v 23.9
seconds after rupture begins on the Black Hills fault Rayleigh wave
carrying energy to Pahrump Rayleigh wave carrying energy to Pahrump
Much energy left behind in soft geologic basins Much energy left
behind in soft geologic basins LV H H FM BH J. Louie, NMSLC
3/3/2011
Slide 26
Adding Physics Cue up and play: BH-ClarkCo-0.5Hz.m4v 45.2
seconds after rupture begins on the Black Hills fault Rock areas
like FM insulated from shaking Rock areas like FM insulated from
shaking Shaking trapped in basins, radiating out Shaking trapped in
basins, radiating out LV H H FM BH J. Louie, NMSLC 3/3/2011
Slide 27
Black Hills M6.5 Scenario Results Max Peak Ground Velocity
(PGV) >140 cm/sec PGV over 60 cm/sec (yellow) bleeds into LVV by
Railroad Pass Large event for a short fault Geologists are divided
on likelihood Geologists are divided on likelihood Need to know how
likely J. Louie, NMSLC 3/3/2011
Slide 28
Frenchman Mountain Fault M6.7 Scenario Possible Scarp in
Neighborhood Event Inside the LVV Basin J. Louie, NESC
2/9/2011
Slide 29
Frenchman Mountain Fault M6.7 Scenario Event Inside the LVV
Basin Cue up and play: FMF_ClarkCo_0.5Hz_24fps.m4v Timelapse
animation 60 seconds wave propagation compressed to 24 sec video
Time compression factor of 2.5 J. Louie, NMSLC 3/3/2011
Slide 30
2-Segment Frenchman Mtn. Fault M6.7 J. Louie, NESC
2/9/2011
Slide 31
2-Segment Frenchman Mtn. Fault M6.7 All of Las Vegas Valley
shakes as hard as Wells in 2008 (20 cm/s) Higher shaking in areas
of refraction and focusing Less shaking in west Valley: stiffer
soil J. Louie, NMSLC 3/3/2011
Slide 32
We Are Computing Dozens of Scenarios J. Louie, NESC
2/9/2011
Slide 33
J. Louie, NMSLC 3/3/2011 Combine the Scenarios
Probabilistically = annual frequency of exceeding ground motion u 0
rate(M, source j ) = annual rate of occurrence for an earthquake
with magnitude M at source location j P = probability of ground
motions u u 0 at site i, if an earthquake occurs at source location
j with magnitude M
Slide 34
US Geological Survey Hazard Maps On line at http://earthquake.
usgs.gov/hazards / http://earthquake. usgs.gov/hazards /
http://earthquake. usgs.gov/hazards / Mostly from past earthquakes
No wave physics J. Louie, NMSLC 3/3/2011
Slide 35
Faul t
Slide 36
Model Setup Two Basin-Thickness Datasets: Widmer et al., 2007
Washoe Co. gravity model Saltus and Jachens 1995 gravity model Two
Geotech Datasets: Pancha 2007 ANSS station measurements Scott et
al., 2004 shallow shear-velocity transect Scenario Fault (like 2008
Wells): Strike: N-S Motion: Normal- down to the west Length: 7.58
km M w : 5.94 (Anderson et al., 1996) Frequency: 0.1 Hz and 1.0
Hz
Slide 37
Physics-Based Wave Propagation 0.1 Hz Model1.0 Hz Model Cue up
and play DowntownReno-1Hz-5.04M.m4v The basin amplifies and traps
seismic shaking Wave propagation unaffected by basin dataset
boundaries in the 0.1 Hz Model Wave propagation is affected by
basin dataset boundaries in the 1.0 Hz Model- but not in basin