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Published February 2014 | Published
Journal Article Open

Experimental investigation of strong ground motion due to thrust fault earthquakes


Thrust fault earthquakes are studied in a laboratory earthquake setup previously used to investigate analog strike-slip seismic events. Dynamic mode II ruptures are generated along preexisting faults in an analog material, Homalite H-100, and their interaction with the free surface is studied for both sub-Rayleigh and supershear rupture speeds. High-speed digital photography and laser velocimeter diagnostics are used synergistically to identify and study the ground velocity signatures caused by the various features of the generated ruptures. The obtained surface-normal motions of both sub-Rayleigh and supershear ruptures show substantial asymmetry between the hanging and footwall, with the hanging wall experiencing much larger velocity amplitudes. The main features of the surface velocity traces at various stations can be explained by the calculated arrivals of various waves and fronts—Mach cones, Pand S waves, and sub-Rayleigh features. In both the sub-Rayleigh and supershear cases, the arrival of the rupture tip generates a prominent Rayleigh wave traveling along the simulated Earth's surface. Supershear events feature larger amplitudes of ground shaking profiles. All signatures in the surface motion records attenuate and broaden with increasing distance from the fault trace. The signatures corresponding to the arrival of the Mach fronts attenuate with distance at a slower rate than those from sub-Rayleigh ruptures. The arrival of the updip supershear rupture at the free surface creates a downdip propagating slip feature with its own Mach cone. These additional Mach fronts further amplify ground shaking on the hanging and footwalls.

Additional Information

© 2013 American Geophysical Union. Received 6 Jun 2013; Accepted 4 Dec 2013; Accepted article online 17 Dec 2013; Published online 26 Feb 2014. This study was supported by the National Science Foundation (grant EAR 1142183) and the Southern California Earthquake Center (SCEC). SCEC is funded by NSF Cooperative Agreement EAR-0529922 and U.S. Geological Survey Cooperative Agreement 07HQAG0008. The SCEC contribution number for this paper is 1767.

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August 22, 2023
August 22, 2023