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Mitigating artifacts in back-projection source imaging with implications for frequency-dependent properties of the Tohoku-Oki earthquake

Meng, Lingsen and Ampuero, Jean-Paul and Luo, Yingdi and Wu, Wenbo and Ni, Sidao (2013) Mitigating artifacts in back-projection source imaging with implications for frequency-dependent properties of the Tohoku-Oki earthquake. Earth Planets and Space, 64 (12). pp. 1101-1109. ISSN 1343-8832. doi:10.5047/eps.2012.05.010.

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Comparing teleseismic array back-projection source images of the 2011 Tohoku-Oki earthquake with results from static and kinematic finite source inversions has revealed little overlap between the regions of high- and low-frequency slip. Motivated by this interesting observation, back-projection studies extended to intermediate frequencies, down to about 0.1 Hz, have suggested that a progressive transition of rupture properties as a function of frequency is observable. Here, by adapting the concept of array response function to non-stationary signals, we demonstrate that the "swimming artifact", a systematic drift resulting from signal non-stationarity, induces significant bias on beamforming back-projection at low frequencies. We introduce a "reference window strategy" into the multitaper-MUSIC back-projection technique and significantly mitigate the "swimming artifact" at high frequencies (1 s to 4 s). At lower frequencies, this modification yields notable, but significantly smaller, artifacts than time-domain stacking. We perform extensive synthetic tests that include a 3D regional velocity model for Japan. We analyze the recordings of the Tohoku-Oki earthquake at the USArray and at the European array at periods from 1 s to 16 s. The migration of the source location as a function of period, regardless of the back-projection methods, has characteristics that are consistent with the expected effect of the "swimming artifact". In particular, the apparent up-dip migration as a function of frequency obtained with the USArray can be explained by the "swimming artifact". This indicates that the most substantial frequency-dependence of the Tohoku-Oki earthquake source occurs at periods longer than 16 s. Thus, low-frequency back-projection needs to be further tested and validated in order to contribute to the characterization of frequency-dependent rupture properties.

Item Type:Article
Related URLs:
URLURL TypeDescription
Meng, Lingsen0000-0003-2428-0548
Ampuero, Jean-Paul0000-0002-4827-7987
Luo, Yingdi0000-0002-1165-6107
Wu, Wenbo0000-0002-6249-8065
Ni, Sidao0000-0003-2988-4850
Additional Information:© 2013 The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS); The Seismological Society of Japan; The Volcanological Society of Japan; The Geodetic Society of Japan; The Japanese Society for Planetary Sciences; TERRAPUB. Received December 27, 2011; Revised May 4, 2012; Accepted May 17, 2012; Online published January 28, 2013. This research was supported by NSF grant EAR-1015704, by the Gordon and Betty Moore Foundation and by the Southern California Earthquake Center, which is funded by NSF Cooperative Agreement EAR-0106924 and USGS Cooperative Agreement 02HQAG0008. The EarthScope USArray and the European ORFEUS data center were used to access the data. This paper is Caltech Tectonics Observatory contribution #198 and Caltech Seismolab contribution #10075.
Group:Caltech Tectonics Observatory, Seismological Laboratory
Funding AgencyGrant Number
Gordon and Betty Moore FoundationUNSPECIFIED
Southern California Earthquake Center (SCEC)UNSPECIFIED
Subject Keywords:Back-projection; Tohoku-Oki earthquake; frequency-dependent rupture properties; MUSIC; swimming artifact
Other Numbering System:
Other Numbering System NameOther Numbering System ID
Caltech Tectonics Observatory198
Caltech Division of Geological and Planetary Sciences10075
Issue or Number:12
Record Number:CaltechAUTHORS:20130308-073907285
Persistent URL:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:37398
Deposited By: Tony Diaz
Deposited On:15 Apr 2013 19:00
Last Modified:09 Nov 2021 23:28

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