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J. Louie UNR Geol492/692 Spring 2005 Using Refraction Microtremor reconnaissance: Rapid surveys take advantage of urban noise More details at www.seismo.unr.edu/hazsurv Surveying Seismic Microzonation in Urban Areas Slide 2 J. Louie UNR Geol492/692 Spring 2005 Surface waves show different velocities at different frequencies but only after some distance. Refraction Microtremor for Shallow Shear Velocity Initial funding from SCEC, UNR, VUW, Optim LLC Raw Data >14 Hz Filter J. Louie UNR Geol492/692 Spring 2005 Transect Data High-velocity picks at >0.4 sec period are unreliable. Picks at 0.1-0.3 sec illustrate velocity differences to 100 m depth. Slide 37 J. Louie UNR Geol492/692 Spring 2005 Some correlation to faulting, soil type? Las Vegas Transect Slide 38 J. Louie UNR Geol492/692 Spring 2005 Geologic Info to Predict V s NSL, July 03, sponsored by LLNL Can soil maps predict V s ? Slide 39 J. Louie UNR Geol492/692 Spring 2005 Does extrapolating V s work? V s assigned to soil-map units using central-City measurements. Later, outlying measurements (B. Luke, UNLV) not predicted by maps. Slide 40 J. Louie UNR Geol492/692 Spring 2005 Does extrapolating V s work? V s assigned to soil-map units using central-City measurements. Later, outlying measurements (B. Luke, UNLV) not predicted by maps. 1 2 3 4 Slide 41 J. Louie UNR Geol492/692 Spring 2005 Most of Strip, Downtown; south side of Valley only 79 sites total 1000 well logs & geologic mapping Las Vegas Transect Slide 42 J. Louie UNR Geol492/692 Spring 2005 How to Extrapolate Shallow V s Correlate 75 Vs measurements against stratigraphic model. Stratigraphy interpolated between >500 water-well logs. Slide 43 J. Louie UNR Geol492/692 Spring 2005 Extrapolated vs. Measured Comparisons along Cheyenne-to-Tropicana transect. Slide 44 J. Louie UNR Geol492/692 Spring 2005 No correlation between V 30 and geologic map. Las Vegas Transect Slide 45 J. Louie UNR Geol492/692 Spring 2005 Correlation with clay soils, caliche in Las Vegas? Las Vegas Transect Slide 46 J. Louie UNR Geol492/692 Spring 2005Summary ReMi allows rapid seismic shaking-hazard classification, as required by IBC2000. Long ReMi transects can geophysically characterize spatial variations in shaking hazard. Mapped soil and geologic units do not reliably predict the measured V 30. Our measurements suggest one can use river gradients, Quaternary thickness, or alluvial fan composition to predict shallow velocities. Slide 47 J. Louie UNR Geol492/692 Spring 2005 Example of public outreach: Discoveries and Breakthroughs Inside Science, news shorts funded by AIP, AGU, etc.Outreach 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.