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Title: Earthquake Source Complexity Controls the Frequency Dependence of Near‐Source Radiation Patterns
Abstract

The spatial patterns of earthquake ground motion amplitudes are commonly represented using a double‐couple model that corresponds to shear slip on a planar fault. While this framework has proven largely successful in explaining low‐frequency seismic recordings, at higher frequencies the wavefield becomes more azimuthally isotropic for reasons that are not yet well understood. Here, we use a dense array of nodal seismometers in Oklahoma to study the radiation patterns of earthquakes in the near‐source region where the effects of wavefield scattering are limited. At these close distances, the radiation pattern is predominantly double couple at low frequencies (<15 Hz). At higher frequencies, the recorded wavefield contains significant isotropic and residual components that cannot be explained as path or site effects, implying complexity in the rupture process or local fault zone structure. These findings demonstrate that earthquake source complexity can drive variability in the ground motions that control seismic hazard.

 
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NSF-PAR ID:
10360686
Author(s) / Creator(s):
 ;  ;  
Publisher / Repository:
DOI PREFIX: 10.1029
Date Published:
Journal Name:
Geophysical Research Letters
Volume:
48
Issue:
17
ISSN:
0094-8276
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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