Seismic Imaging beneath an InSAR Anomaly in Eastern Washington State: Shallow Faulting Associated with an Earthquake Swarm in a Low‐Hazard Area

• DOI: 10.1785/0120150295
• Publication Date: 2016-07-25T15:08:12Z
• Authors: W. J. Stephenson; J. K. Odum; C. W. Wicks; T. L. Pratt; R. J. Blakely
• Keywords: Anomaly (physics)

In 2001, a rare swarm of small, shallow earthquakes beneath the city Spokane, Washington, caused ground shaking as well audible booms over five‐month period. Subsequent Interferometric Synthetic Aperture Radar (InSAR) data analysis revealed an area surface uplift in vicinity earthquake swarm. To investigate potential faults that may have both and topographic uplift, we collected ∼3 km high‐resolution seismic‐reflection profiles to image upper‐source region The two reveal complex deformational pattern within Quaternary alluvial, fluvial, flood deposits, underlain by Tertiary basalts basin sediments. At least 100 m arching on basalt upper 500 m is interpreted from seismic magnetic modeling. Two west‐dipping deform sediments project near location Spokane fault defined modeling InSAR data.