Please use this identifier to cite or link to this item: https://hdl.handle.net/10356/143279
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dc.contributor.authorZeng, Hongyuen_US
dc.contributor.authorWei, Shengjien_US
dc.contributor.authorWu, Wenboen_US
dc.date.accessioned2020-08-18T09:02:57Z-
dc.date.available2020-08-18T09:02:57Z-
dc.date.issued2020-
dc.identifier.citationZeng, H., Wei, S., & Wu, W. (2020). Sources of uncertainties and artefacts in back-projection results. Geophysical Journal International, 220 (2), 876-891. doi:10.1093/gji/ggz482en_US
dc.identifier.issn0956-540Xen_US
dc.identifier.urihttps://hdl.handle.net/10356/143279-
dc.description.abstractBack-projecting high-frequency (HF) waves is a common procedure for imaging rupture processes of large earthquakes (i.e. Mw > 7.0). However, obtained back-projection (BP) results could suffer from large uncertainties since high-frequency seismic waveforms are strongly affected by factors like source depth, focal mechanisms, and the Earth's 3-D velocity structures. So far, these uncertainties have not been thoroughly investigated. Here, we use synthetic tests to investigate the influencing factors for which scenarios with various source and/or velocity set-ups are designed, using either Tohoku-Oki (Japan), Kaikoura (New Zealand), Java/Wharton Basin (Indonesia) as test areas. For the scenarios, we generate either 1-D or 3-D teleseismic synthetic data, which are then back-projected using a representative BP method, MUltiple SIgnal Classification (MUSIC). We also analyse corresponding real cases to verify the synthetic test results. The Tohoku-Oki scenario shows that depth phases of a point source can be back-projected as artefacts at their bounce points on the earth's surface, with these artefacts located far away from the epicentre if earthquakes occur at large depths, which could significantly contaminate BP images of large intermediate-depth earthquakes. The Kaikoura scenario shows that for complicated earthquakes, composed of multiple subevents with varying focal mechanisms, BP tends to image subevents emanating large amplitude coherent waveforms, while missing subevents whose P nodal directions point to the arrays, leading to discrepancies either between BP images from different arrays, or between BP images and other source models. Using the Java event, we investigate the impact of 3-D source-side velocity structures. The 3-D bathymetry together with a water layer can generate strong and long-lasting coda waves, which are mirrored as artefacts far from the true source location. Finally, we use a Wharton Basin outer-rise event to show that the wavefields generated by 3-D near trench structures contain frequency-dependent coda waves, leading to frequency-dependent BP results. In summary, our analyses indicate that depth phases, focal mechanism variations and 3-D source-side structures can affect various aspects of BP results. Thus, we suggest that target-oriented synthetic tests, for example, synthetic tests for subduction earthquakes using more realistic 3-D source-side velocity structures, should be conducted to understand the uncertainties and artefacts before we interpret detailed BP images to infer earthquake rupture kinematics and dynamics.en_US
dc.description.sponsorshipMinistry of Education (MOE)en_US
dc.description.sponsorshipNational Research Foundation (NRF)en_US
dc.language.isoenen_US
dc.relation.ispartofGeophysical Journal Internationalen_US
dc.rights© 2019 The Author(s). Published by Oxford University Press on behalf of The Royal Astronomical Society. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.en_US
dc.subjectScience::Geologyen_US
dc.titleSources of uncertainties and artefacts in back-projection resultsen_US
dc.typeJournal Articleen
dc.contributor.researchEarth Observatory of Singaporeen_US
dc.identifier.doi10.1093/gji/ggz482-
dc.description.versionPublished versionen_US
dc.identifier.scopus2-s2.0-85085362506-
dc.identifier.issue2en_US
dc.identifier.volume220en_US
dc.identifier.spage876en_US
dc.identifier.epage891en_US
dc.subject.keywordsBody Wavesen_US
dc.subject.keywordsComputational Seismologyen_US
dc.description.acknowledgementThis project is supported by the Earth Observatory of Singapore grant (M4430255). All seismic data and the station codes are collected through the Data Management Center of the Incorporated Research Institutions for Seismology (IRIS), using Wilber 3. All the figures are plotted using the Generic Mapping Tools (GMT), and the Python Matplotlib package. The seismic data are processed using the Python package, Obspy and the waveforms are aligned and selected using the Python package, aimbat (Lou et al. 2013). We thank Pavel Adamek for his help in clarifying and improving several aspects of the writing. We appraciate comments and suggestions from Jiuxun Yin, Zengxi Ge and editors, which help to improve the quality and presentation of the manuscript. This work comprises Earth Observatory of Singapore contribution no. 268. This research is partly supported by the National Research Foundation Singapore and the Singapore Ministry of Education under the Resarch Centers of Excellence initiative.en_US
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