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This data release provides a map of the time-averaged shear-wave velocity in the upper 30 m (Vs30) for California using the method described by Thompson and others (2014). There are two adjustments to the algorithm described by Thompson and others (2014), which is built on the geology-based Vs30 map by Wills and Clahan (2006). In this data release, we use the Wills and others (2015) updated geology-based Vs30 map. The second change is that we have adjusted the kriging procedure so that measured Vs30 values do not affect the predictions across distinctly different geologic units. July 2022 Update (ver. 2.0) Resolution is now 3 arcseconds instead of 7.5 arcseconds Fixed a code error that prevented some of the Vs30...
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A helicopter-borne electromagnetic/magnetic survey was flown over the Stillwater area, southwest Montana from May 5 to May 16, 2000. The survey was conducted over the Stillwater Igneous Complex, a Precambrian layered mafic-ultramafic intrusion which is characterized by igneous layering. Electromagnetic data were acquired using DIGHEM helicopter-borne electromagnetic system. Magnetic data were collected with optically pumped Cesium Vapor Geometrics G822 magnetometer. Sensor elevation above ground was measured with Honeywell/Sperry AA220 radar. The nominal elevation of the sensor was 60 meters. Survey coverage comprises 1,914 line kilometers, including tie lines. Flight lines were flown in an azimuthal direction of...
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Controlled source audio-frequency magnetotellurics (CSAMT) data were collected over the Sevier fault, near Red Knoll in Kane county Utah, to better understand the hydrogeology of the area. CSAMT data provide vertical cross-section (profile) data about the resistivity of the subsurface, which may be related to lithologic boundaries and (or) grain-size distribution in the subsurface. CSAMT involves transmitting a current at various frequencies in one location, and measuring resistivity differences between electrodes spaced along a receiver line several kilometers from the transmitter. Data were collected using a GGT-30 transmitter and GDP32-II receiver (Zonge international. Inc.). Data processing and inversions were...
    map background search result map search result map An Updated Vs30 Map for California with Geologic and Topographic Constraints (ver. 2.0, July 2022) Airborne electromagnetic and magnetic survey data, Stillwater Complex, Montana, May 2000 (ver. 2.0, June 2020) Controlled source audio-frequency magnetotellurics (CSAMT) data from the Sevier fault near Red Knoll, Kane County, Utah (ver. 2.0, July 2022) Controlled source audio-frequency magnetotellurics (CSAMT) data from the Sevier fault near Red Knoll, Kane County, Utah (ver. 2.0, July 2022) Airborne electromagnetic and magnetic survey data, Stillwater Complex, Montana, May 2000 (ver. 2.0, June 2020) An Updated Vs30 Map for California with Geologic and Topographic Constraints (ver. 2.0, July 2022)