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Exploring the relation between backprojection images and earthquake source processes
  • Jiuxun Yin,
  • Marine Denolle
Jiuxun Yin

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Marine Denolle
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Abstract

Backprojection (BP) of teleseismic P waves is a widely-used method to study the evolution of earthquake radiation and is particularly effective for large earthquakes. We can harness key information on the spatiotemporal evolution during the rupture process from waveform similarity or coherency. Understanding the relation between earthquake physics and the spatiotemporal evolution from BP imaging, which are usually obtained from high frequency seismic waveforms, is of great importance. Theoretical studies indicate that the high-frequency bursts can be related to abrupt changes in rupture velocity (e.g. stopping of rupture or kinks on the fault). Moreover, the BP images are thought to be equivalent to either slip or slip rate on the fault, provided that the Green’s functions from the sources to the receivers are incoherent delta functions. Furthermore, recent studies propose that the frequency dependent features of BP results can reflect the stress status, frictional and/or geometrical heterogeneity on the fault surface. It is promising that we can obtain more observational constraints and information about the earthquake dynamic source from the backprojection results combined with other independent techniques. In this study, we attempt to figure out the relation between the BP results and earthquake source process by testing both kinematic and dynamic source models. With these source models, we can synthesise the seismic waveforms and trace them back to the fault surface using the BP method. Therefore, we can directly compare the BP results with the already-known earthquake sources and further explore the possible relation to the source properties by varying our source models such as the friction laws, fault geometries. To simplify our problem and exclude the potential effects from complex earth structure, our tests are carried out in a purely elastic medium, whole space, allowing us to solve analytically for the far-field body waves. From these systematical tests and comparisons, we aim at building a comprehensive relation between the BP images and various source properties. Moreover, our results can provide significant help to better understand the physics of earthquake source process from seismic observations.