Imaging the Coso geothermal area crustal structure with an array of high-density mini-arrays

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Conference Proceedings: Imaging the Coso geothermal area crustal structure with an array of high-density mini-arrays

Advances in passive seismic data collecting and processing have produced higher resolution images of the crust and mantle than have been previously obtainable. The Earth is appearing to be more heterogeneous than was thought when only rougher scale observations were available. Here we present results from a dense array of passive seismometers that show considerable variations in the crust over distances as short as 10 km and compare these results to what is observable with less densely spaced instruments. We utilize data collected during the 18-month deployment of 16 dense mini-arrays in the region of the China Lake geothermal field near Ridgecrest, CA. We image the crustal structure within the geothermal field, its relationship to regional tectonic features, and search for an indication of mantle influence on volcanism. The mini-arrays consist of mostly short period instruments arranged in orthogonal line arrays with 1/2-km station spacing. The average distance between each array is approximately 5 km. We calculate 375 good quality mini-array beamed receiver functions for teleseismic events. Using array-processing techniques, we mitigate the effects of near surface scattered energy. Mini-arrays of seismometers allow for imaging of small-scale crustal structures, as scattered energy will decorrelate across the array while arrivals from converted phases stack coherently. Combining data from all arrays we process the data set as an array of mini-arrays and stack the data into CCP bins. Processing the data in this manner allows us to observe lateral variations in subsurface structures such as mid-crustal features and the Moho within the nearly 40 by 40 km area of sampling. We find extremely complex crustal structure in this region, including many converters dipping nearly 15 degrees and over 8 km of topography on the Moho. It is likely that complex, non-planar interfaces produce artifacts in our CCP stacks, and to accurately image complex crustal structure we perform backprojection migration. By migrating the data recorded by the group of mini-arrays we produce a fine scale image of the crust that is minimally contaminated by scattering artifacts.

Gilbert, H.J.; Wilson, C.K. ; Jones, C.H.; Sheehan and A.F. 

Eos, Transactions, American Geophysical Union, 11/1/2000

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Gilbert, H.J.; Wilson, C.K. ; Jones, C.H.; Sheehan, A.F. . 11/1/2000. Imaging the Coso geothermal area crustal structure with an array of high-density mini-arrays. Proceedings of (!) ; (!) : Eos, Transactions, American Geophysical Union.

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