Surveying Seismic Microzonation in Urban Areas

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Surveying Seismic Microzonation in Urban Areas

• Using Refraction Microtremor reconnaissance
• Rapid surveys take advantage of urban noise
• More details at www.seismo.unr.edu/hazsurv

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Refraction Microtremor for Shallow Shear Velocity
ReMi measures Rayleigh dispersion with linear
refraction arrays (paper by Louie, April 2001
BSSA).
Initial funding from SCEC, UNR, VUW, Optim LLC
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Refraction Microtremor for Shallow Shear Velocity
ReMi has classified hard and soft sites around
the world by measuring V30, average shear
velocity to 30 m depth.
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Reno Transect
Local reconnaissance was first test.
Supported by UNR and IRIS-PASSCAL
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Reno Transect
Unexpected results high V30 in active alluvium.
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Reno Transect
Lack of V30 correlation to geologic or soil maps
Only Tertiary Andesite (Ta) shows a
characteristic V30
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The First Reno Hazard Map
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Shallow Shear-Velocity Transects
July 2003 San Gabriel Valley Los Angeles
Transect mapped on NEHRP hazard class map by
Wills, from SCEC Phase 3 Report
Supported by USGS, NEHRP ERP and IRIS-PASSCAL
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Los Angeles Transect
200 shallow Vs profiles from San Gabriel Riv.
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Los Angeles Transect
No V30 correlation with active vs. older
alluvium R2 0.2!
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Shallow Shear-Velocity Transects
Las Vegas route from Cheyenne to Tropicana
3-km-deep basin
1-km-deep basin
Supported by DOE-LLNL and IRIS-PASSCAL
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Las Vegas Transect
Some correlation to faulting, soil type?
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Las Vegas Transect
No correlation between V30 and geologic map.
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Las Vegas Transect
Correlation with clay soils, caliche in Las Vegas?
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Las Vegas Transect
Shallow section V100 hint at stratigraphy,
faulting?
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A Preliminary Las Vegas Hazard Map
Transect V30 values correlated with soil-map
units across 4 quadrangles in Las Vegas Valley
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Outreach
Example of public outreach Discoveries and
Breakthroughs Inside Science, news shorts funded
by AIP, AGU, etc.
KFSN-TV Fresno, CA KGBT-TV Harlingen, TX KJTV-TV
Lubbock, TX KTRK-TV Houston, TX KNBC-TV Burbank,
CA KNSD-TV San Diego, CA KQTV-TV St. Joseph,
MO KNTV-TV San Francisco, CA KRQE-TV Albuquerque,
NM KTSM-TV El Paso, TX KTVN-TV Reno, NV KWQC-TV
Davenport, IA KXAS-TV Fort Worth, TX WAGM-TV
Presque Isle, ME WTEN-TV Albany, NY WCAU-TV
Philadelphia, PA WCMH-TV Columbus, OH WCYB-TV
Bristol, VA WEWS-TV Cleveland, OH WFTS-TV Tampa,
FL WLUK-TV Green Bay, WI WBBH-TV Fort Myers, FL
WHIO-TV Dayton, OH WIS-TV Columbia, SC WJAR-TV
Cranston, RI WLBT-TV Jackson, MS WMAQ-TV
Chicago,IL WNBC-TV New York, NY WNCN-TV Raleigh,
NC KTSM-TV Omaha, NE WPBN-TV Traverse City,
MI WSYM-TV Lansing, MI WTVJ-TV Miami, FL WVIT-TV
Hartford, CT WVTM-TV Birmingham, AL WXYZ-TV
Southfield, MI WJXT-TV Jacksonville, FL WTXL-TV
Tallahassee, FL WIVT-TV Binghamton, NY WEVV-TV
Evansville, IN WCJB-TV Gainesville, FL WPXI-TV
Pittsburgh, PA CHAT-TV Medicine Hat, ALB
K. Heineman, NewsProNet, Producers
Technology Transfer Commercial ReMi is now in
use by geotechnical consultants and agencies
worldwide.