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An M_w = 7.7 slow earthquake in 1960 near the Aysén Fjord region, Chile

Kanamori, Hiroo and Rivera, Luis (2017) An M_w = 7.7 slow earthquake in 1960 near the Aysén Fjord region, Chile. Geophysical Journal International, 211 (1). pp. 93-106. ISSN 0956-540X. doi:10.1093/gji/ggx292.

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We re-examine the source characteristics of an M_s = 6.9 earthquake in Chile which occurred on 1960 June 6, near the Aysén Fjord region where a remarkable earthquake swarm occurred in 2007 with more than 7000 earthquakes and hundreds of landslides. The June 6 event occurred during the aftershock activity of the 1960 May 22, M_w = 9.5 great Chilean earthquake. A recently found well-calibrated strain seismogram of the June 6 event recorded at Isabella (ISA), California, is the impetus to this study. We confirm that this event is a slow earthquake caused by a source process extending at least 190 s with a seismic moment of M_0 = 4.5 × 10^(20) N⋅m (M_w = 7.7). Although the mechanism cannot be uniquely determined, an NS trending right-lateral strike-slip mechanism is consistent with the ISA record. The depth cannot be constrained well, but the slowness of the event suggests that it may have occurred in a somewhat deeper high-temperature ductile environment caused by nearby subduction of the Chile Rise. The mechanism and the proximity of this event to the Liquiñe-Ofqui fault (LOF) which extends north–south over 1000 km along the Chilean coast suggest that the June 6 event represents a slip on this fault. The large moment of the June 6 event indicates strong interaction between the Nazca-South American plate boundary and the LOF with significant slip partitioning.

Item Type:Article
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URLURL TypeDescription
Kanamori, Hiroo0000-0001-8219-9428
Rivera, Luis0000-0002-0726-5445
Additional Information:© 2017 The Authors. Published by Oxford University Press on behalf of The Royal Astronomical Society. Accepted 2017 July 12. Received 2017 July 3; in original form 2017 March 15. Published: 14 July 2017. Dr Stewart Smith kindly sent us the original ISA strip-chart record of the 1960 May 22, M_w = 9.5 earthquake, which he has carefully kept in good condition. Availability of this record is the impetus to our study which almost entirely depends on this invaluable record. Dr Guy Masters provided us with the hand-digitized data of the ISA strain record. Dr Joann Stock introduced us to the literature on the recent investigations on the Aysén swarm. Dr Shingo Watada provided us with the Tsukuba IGY seismograms. We used a program written by Dr Duncan Agnew for computing tidal variations at ISA, California and Ñaña, Peru. Dr Sergio Barrientos provided us with the information on the 1960 June 6, event. We used Syngine web service at the Data Management Center of Incorporate Research Institutions for Seismology for computing some of the synthetic seismograms. We thank the two anonymous reviewers for their careful review.
Group:Seismological Laboratory
Subject Keywords:South America, Earthquake dynamics, Earthquake source observations, Surface waves and free oscillations, Dynamics and mechanics of faulting
Issue or Number:1
Record Number:CaltechAUTHORS:20171020-081818146
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Official Citation:Hiroo Kanamori, Luis Rivera; An Mw = 7.7 slow earthquake in 1960 near the Aysén Fjord region, Chile, Geophysical Journal International, Volume 211, Issue 1, 1 October 2017, Pages 93–106,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:82533
Deposited By: Tony Diaz
Deposited On:20 Oct 2017 17:24
Last Modified:15 Nov 2021 19:51

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