Quantifying Site Effects and Their Influence on Earthquake Source Parameter Estimations Using a Dense Array in Oklahoma

被引:8
作者
Chang, Hilary [1 ]
Abercrombie, Rachel E. [2 ]
Nakata, Nori [1 ,3 ]
Pennington, Colin N. [4 ]
Kemna, Kilian B. [5 ]
Cochran, Elizabeth S. [6 ]
Harrington, Rebecca M. [5 ]
机构
[1] MIT, Dept Earth Atmospher & Planetary Sci, Cambridge, MA 02139 USA
[2] Boston Univ, Dept Earth & Environm, Boston, MA USA
[3] Lawrence Berkeley Natl Lab, Berkeley, CA USA
[4] Lawrence Livermore Natl Lab, Livermore, CA USA
[5] Ruhr Univ Bochum, Bochum, Germany
[6] US Geol Survey, Earthquake Sci Ctr, Pasadena, CA USA
关键词
earthquake source; ground motion; site effects; uncertainty quantification; stress drop; GREENS-FUNCTION ANALYSIS; STRESS DROP; GROUND-MOTION; CALIFORNIA; ATTENUATION; FREQUENCY; SPECTRA; KAPPA; FAULT; FIELD;
D O I
10.1029/2023JB027144
中图分类号
P3 [地球物理学]; P59 [地球化学];
学科分类号
0708 ; 070902 ;
摘要
We investigate the effects of site response on source parameter estimates using earthquakes recorded by the LArge-n Seismic Survey in Oklahoma (LASSO). While it is well known that near-surface unconsolidated sediments can cause an apparent breakdown of earthquake self-similarity, the influence of laterally varying site conditions remains unclear. We analyze site conditions across the 1825-station array on a river plain within an area of 40 km by 23 km using vertical ground motions from 14 regional earthquakes. While the source radiation pattern controls P-wave ground motions below 8 Hz, the surface geology correlates with P-wave ground motions above 8 Hz and S-wave ground motions at 2-21 Hz. Stations installed in alluvial sediments have vertical ground motions that can exceed three times the array median. We use the variation of ground motion of regional earthquakes across the array as a proxy for site effects. The corner frequencies and stress drops of local earthquakes (ML = 0.01-3) estimated using a standard single-spectra approach show negative correlations with the site-effect proxy, while the seismic moments show positive correlations. In contrast, the spectral-ratio approach effectively shows no correlation. The overall bias is small as expected for this relatively homogeneous structure; accurate estimation of site-related biases requires at least 30 stations. Correcting for site-related biases reduces the standard deviations of the source parameters by less than 13% of the total variations. Remaining variations are partially associated with source directivity and model misfits- as small earthquakes can have complex ruptures.
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页数:19
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