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Magnitude of the 1920 Haiyuan earthquake reestimated using seismological and geomorphological methods

Abstract:
Reported magnitudes ranging between 7.8 and 8.7 highlight a confusion about the true size of the 1920 Haiyuan earthquake, the largest earthquake recorded in the northeast Tibetan Plateau. We compiled a global data set of previously unlooked‐at historical seismograms and performed modern computational analyses on the digitized seismic records. We found the epicenter to be near Haiyuan town and obtained a moment magnitude of MW=7.9±0.2. Following traditional approaches, we obtained mB=7.9±0.3 with data from 21 stations and MS(20)=8.1±0.2 with data from three stations. Geomorphologically, we mapped the surface rupture and horizontal offsets on high‐resolution Pleiades satellite and drone imagery that covered the entire western and middle sections of the 1920 Haiyuan earthquake rupture and compiled offsets reported on the eastern section from field measurements in the 1980s. Careful discrimination between single‐event and cumulative offsets suggests average horizontal slips of 3.0±1.0 m on the western section, 4.5±1.5 m on the middle section, and 3.5±0.5 m on the eastern section, indicating a total moment magnitude of MW=7.8±0.1. Thus, the seismological and geomorphological results agree within the uncertainties, a weighted average giving a moment magnitude of MW=7.9±0.2 for the 1920 Haiyuan earthquake. It is likely that earthquake magnitudes based on the historical M were systematically overestimated.
Publication status:
Published
Peer review status:
Peer reviewed

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Publisher copy:
10.1029/2019JB019244

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More by this author
Institution:
University of Oxford
Division:
MPLS
Department:
Earth Sciences
Role:
Author
More by this author
Institution:
University of Oxford
Division:
MPLS
Department:
Earth Sciences
Role:
Author
More by this author
Institution:
University of Oxford
Division:
MPLS
Department:
Earth Sciences
Role:
Author
More by this author
Institution:
University of Oxford
Division:
MPLS
Department:
Earth Sciences
Role:
Author


Publisher:
American Geophysical Union
Journal:
Journal of Geophysical Research: Solid Earth More from this journal
Volume:
125
Issue:
8
Article number:
e2019JB019244
Publication date:
2020-08-13
Acceptance date:
2020-07-06
DOI:
EISSN:
2169-9313
ISSN:
2169-9356


Language:
English
Keywords:
Pubs id:
1115901
Local pid:
pubs:1115901
Deposit date:
2020-07-02

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