Preliminary Results on the 3-dimensional Seismic Structure of the Lithosphere under the USGS Central California Seismic Array |
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| Authors: | Eystein S Husebye ers Christoffersson Keiiti Aki Christine Powell |
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| Institution: | NTNF/NORSAR, Kjeller, Norway;Applied Seismology Group, Lincoln Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA;Department of Earth and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA;Department of Geological and Geophysical Sciences, Princeton University, Princeton, New Jersey 08540, USA |
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| Abstract: | About 1500 readings of teleseismic P -time residuals obtained from the US Geological Survey seismograph network in central California have been used to obtain a three-dimensional image of seismic velocity anomalies for this area by the method of Aki, Christoffersson & Husebye We found that the California network is less suitable than the LASA and NORSAR arrays for this kind of studies because of its greater proportion of peripheral blocks in which the resolution is very poor for the stochastic inverse solution and the random error effect is severe for the generalized inverse solution. Nevertheless, the resultant velocity anomalies show a remarkable correlation with the San Andreas fault zone to a depth of 75 km. The anomaly pattern changes drastically as the depth exceeds 75 km, suggesting that the asthenosphere has been reached. |
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