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Navigating Earthquake Physics with High-Resolution Array Back-Projection


Meng, Lingsen (2013) Navigating Earthquake Physics with High-Resolution Array Back-Projection. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/Y2C6-YA15.


Understanding earthquake source dynamics is a fundamental goal of geophysics. Progress toward this goal has been slow due to the gap between state-of-art earthquake simulations and the limited source imaging techniques based on conventional low-frequency finite fault inversions. Seismic array processing is an alternative source imaging technique that employs the higher frequency content of the earthquakes and provides finer detail of the source process with few prior assumptions. While the back-projection provides key observations of previous large earthquakes, the standard beamforming back-projection suffers from low resolution and severe artifacts. This thesis introduces the MUSIC technique, a high-resolution array processing method that aims to narrow the gap between the seismic observations and earthquake simulations.

The MUSIC is a high-resolution method taking advantage of the higher order signal statistics. The method has not been widely used in seismology yet because of the nonstationary and incoherent nature of the seismic signal. We adapt MUSIC to transient seismic signal by incorporating the Multitaper cross-spectrum estimates. We also adopt a “reference window” strategy that mitigates the “swimming artifact,” a systematic drift effect in back projection. The improved MUSIC back projections allow the imaging of recent large earthquakes in finer details which give rise to new perspectives on dynamic simulations. In the 2011 Tohoku-Oki earthquake, we observe frequency-dependent rupture behaviors which relate to the material variation along the dip of the subduction interface. In the 2012 off-Sumatra earthquake, we image the complicated ruptures involving orthogonal fault system and an usual branching direction. This result along with our complementary dynamic simulations probes the pressure-insensitive strength of the deep oceanic lithosphere. In another example, back projection is applied to the 2010 M7 Haiti earthquake recorded at regional distance. The high-frequency subevents are located at the edges of geodetic slip regions, which are correlated to the stopping phases associated with rupture speed reduction when the earthquake arrests.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:earthquake source imaging, earthquake source dynamics, back projection, Tohoku-Oki earthquake, Haiti earthquake, Sumatra earthquake
Degree Grantor:California Institute of Technology
Division:Geological and Planetary Sciences
Major Option:Geophysics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Ampuero, Jean-Paul
Thesis Committee:
  • Stock, Joann M. (chair)
  • Avouac, Jean-Philippe
  • Ampuero, Jean-Paul
  • Helmberger, Donald V.
Defense Date:20 August 2012
Non-Caltech Author Email:meng.caltech (AT)
Record Number:CaltechTHESIS:08232012-003426663
Persistent URL:
Related URLs:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:7191
Deposited By: Lingsen Meng
Deposited On:30 Aug 2012 18:45
Last Modified:12 Nov 2021 20:23

Thesis Files

PDF - Final Version
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[img] Image (GIF) (Back projection of Tohoku-Oki earthquake based on the European network (Chapter 2 and Appendix A)) - Supplemental Material
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[img] Image (GIF) (Back projection of Tohoku-Oki earthquake based on the USArray (Chapter 2 and Appendix A) ) - Supplemental Material
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[img] Image (GIF) (Back projection of off-Sumatra earthquake based on the European network (Chapter 3 and Appendix B) ) - Supplemental Material
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[img] Image (GIF) (Back projection of off-Sumatra earthquake based on the Japanese Hi-net (Chapter 3 and Appendix B)) - Supplemental Material
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