| Abstract: | Ground motion records of local and regional events from a portable array are used to investigate the structural causes of variations in ground motion over distances of a few hundred meters to a few kilometers in the sedimentary basin environment of the Santa Clara Valley, California, and its margins. Arrays of portable seismic stations are used to target four study areas with different ground motion patterns: (1) an edge of the alluvial basin extending up onto a marginal ridge (Blossom Hill), (2) a Cenozoic basin with a nearly flat bottom (Cupertino Basin), (3) a long, narrow Cenozoic basin with a steep V profile (Evergreen Basin), and (4) a line perpendicular to the trace of the Hayward fault. Average peak velocities on Blossom Hill from local earthquakes are a factor of 2.5 times higher than nearby valley sites. Three-dimensional (3D) modeling is used to conclude that the majority of the amplification is due to lower shear-wave velocities along a local fault zone (Shannon-Berrocal). Site amplification over the Cupertino Basin in the frequency band 0.5-4 Hz is generally low (less than 2.0 relative to aMesozoic rock site) and spatially uniform. This response is attributed to the shallow, flat-bottomed shape of the basin and the uniform, flat-laying sedimentary fill. In contrast, site amplification in the Evergreen Basin generally exceeds 3.0 and is attributed to the deep, V-shaped geometry of the basin and younger sedimentary fill. 3D waveform modeling shows the elongated shape of the Evergreen Basin causes more efficient trapping of long-period waves for sources along the long axis of the basin. A low-velocity zone is postulated along the Hayward fault with a width between 100 and 200 m, based on elevated site response along the fault trace and 4.5-Hz fault zone guided waves on the horizontal components of stations near the fault. |
| Genre: | Article |
| ProdID: | 70037510 |
| Citation Author: | Hartzell, S.; Ramirez-Guzman, L.; Carver, D.; Liu, P. |
| Citation Contributing Office: | |
| Citation Datum: | |
| Citation Day: | |
| Citation Edition: | |
| Citation Editor: | |
| Citation End Page: | 2286 |
| Citation Issue: | 5 A |
| Citation Keywords: | |
| Citation Language: | English |
| Citation Larger Work Title: | Bulletin of the Seismological Society of America |
| Citation LatN: | |
| Citation LatS: | |
| Citation LonE: | |
| Citation LonW: | |
| Citation Month: | |
| Citation No Pagination: | |
| Citation Number Of Pages: | 23 |
| Citation Online Only Flag: | |
| Citation Phsyical Description: | |
| Citation Projection: | |
| Citation Public Comments: | |
| Citation Publisher: | |
| Citation Series: | |
| Citation Series Code: | |
| Citation Series Number: | |
| Citation Search Results Text: | Short baseline variations in site response and wave-propagation effects and their structural causes: Four examples in and around the santa clara valley, California; 2010; Article; Journal; Bulletin of the Seismological Society of America; Hartzell, S.; Ramirez-Guzman, L.; Carver, D.; Liu, P. |
| Citation Start Page: | 2264 |
| Citation Volume: | 100 |
| Citation Year: | 2010 |
| Type: | citation/reference |
| Text: | Short baseline variations in site response and wave-propagation effects and their structural causes: Four examples in and around the santa clara valley, California; 2010; Article; Journal; Bulletin of the Seismological Society of America; Hartzell, S.; Ramirez-Guzman, L.; Carver, D.; Liu, P. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/outside_thumb.jpg |
| URL (DIGITAL OBJECT IDENTIFIER): | http://dx.doi.org/10.1785/0120090278 |
| Date Other: | Fri, 1 Jan 2010 00:00 -0600 |
| Publisher: | |
