J. Louie 12/10/2003 J. Louie 12/10/2003 Using Refraction Microtremor reconnaissance: Rapid surveys take advantage of urban noise More details at www.seismo.unr.edu/hazsurv QuickTime™ and aMotion JPEG OpenDML decompres Surveying Seismic Surveying Seismic Microzonation in Urban Areas Microzonation in Urban Areas
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J. Louie 12/10/2003J. Louie 12/10/2003
Using Refraction Microtremor reconnaissance: Rapid surveys take advantage of urban noise More details at www.seismo.unr.edu/hazsurv
QuickTime™ and aMotion JPEG OpenDML decompressorare needed to see this picture.
Surveying Seismic Microzonation in Surveying Seismic Microzonation in Urban AreasUrban Areas
J. Louie 12/10/2003J. Louie 12/10/2003
ReMi measures Rayleigh dispersion with linear refraction arrays (paper by Louie, April 2001 BSSA).
Refraction Microtremor for Shallow Shear VelocityRefraction Microtremor for Shallow Shear Velocity
100-m depth resolution
Initial funding from SCEC, UNR, VUW, Optim LLC
J. Louie 12/10/2003J. Louie 12/10/2003
ReMi has classified hard and soft sites around the world by measuring V30, average shear velocity to 30 m depth.
Refraction Microtremor for Shallow Shear VelocityRefraction Microtremor for Shallow Shear Velocity
J. Louie 12/10/2003J. Louie 12/10/2003
Local reconnaissance was first test.Reno TransectReno Transect
Supported by UNR and IRIS-PASSCAL
J. Louie 12/10/2003J. Louie 12/10/2003
Unexpected results: high V30 in active alluvium.Reno TransectReno Transect
West East
Ta
J. Louie 12/10/2003J. Louie 12/10/2003
Lack of V30 correlation to geologic or soil maps
Reno TransectReno Transect
Only Tertiary Andesite (Ta) shows a characteristic V30
J. Louie 12/10/2003J. Louie 12/10/2003
The First Reno Hazard MapThe First Reno Hazard Map
J. Louie 12/10/2003J. Louie 12/10/2003
July 2003 San Gabriel Valley & Los AngelesShallow Shear-Velocity TransectsShallow Shear-Velocity Transects
B
C
D
E
Transect mapped on NEHRP hazard class map by Wills, from SCEC Phase 3 Report
Supported by USGS, NEHRP ERP and IRIS-PASSCAL
J. Louie 12/10/2003J. Louie 12/10/2003
200 shallow Vs profiles from San Gabriel Riv.
Los Angeles TransectLos Angeles Transect
San Gabriel Mts.are C, not B.
Alamitos Bayis D, not E.
V30 may correlate with hydraulic gradient.
J. Louie 12/10/2003J. Louie 12/10/2003
No V30 correlation with active vs. older alluvium; R2 = 0.2!Los Angeles TransectLos Angeles Transect