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Shallow nonvolcanic tremor activity and potential repeating earthquakes in the Chile triple junction; seismic evidence of the subduction of the active Nazca-Antarctic spreading center

Miguel Saez, Sergio Ruiz, Satoshi Ide and Hiroko Sugioka
Shallow nonvolcanic tremor activity and potential repeating earthquakes in the Chile triple junction; seismic evidence of the subduction of the active Nazca-Antarctic spreading center
Seismological Research Letters (July 2019) Pre-Issue Publication

Abstract

In southern Chile, at approximately 46.2 degrees S and approximately 75.2 degrees W, the active spreading center between the Nazca and Antarctic plates is colliding with the South American plate, forming the Chile triple junction (CTJ). For 1 yr, from March 2009 to February 2010, five ocean?bottom seismometers (OBSs) were deployed over the CTJ. We used a portion of the OBS data to study the seismic signatures of the subduction of the active Nazca-Antarctic spreading center. Using the envelope technique, we detected long episodes of shallow nonvolcanic tremor (NVT) activity. To improve the identified location of the NVT activity, we cross-correlated the vertical and horizontal components of all located NVTs. In different months, we measured the local maximum of the lag?time correlation near 2 s, which is associated with the lag between the S and P waves (S-P (sub time) ). Furthermore, we observed that in the days with intense tremor activity, the maxima corresponding to S-P (sub time) emerged in windows without observable NVTs. We suggest that days with intense tremor activity correspond to an almost continuous slow slip, which may accelerate and decelerates nearly randomly, with spatial and temporal heterogeneity. In addition, we detected some potential repeating earthquakes with an S-P (sub time) near 2 s, as well as NVTs. The detected NVT activity and potential repeating earthquakes suggest the existence of a shallow region close to the CTJ that is able to generate brittle (earthquakes) and brittle-ductile (potential repeating earthquakes and NVTs) ruptures.


ISSN: 0895-0695
EISSN: 1938-2057
Serial Title: Seismological Research Letters
Serial Volume: Pre-Issue Publication
Title: Shallow nonvolcanic tremor activity and potential repeating earthquakes in the Chile triple junction; seismic evidence of the subduction of the active Nazca-Antarctic spreading center
Affiliation: University of Chile, Department of Geophysics, Santiago, Chile
Published: 20190724
Text Language: English
Publisher: Seismological Society of America, El Cerrito, CA, United States
References: 33
Accession Number: 2019-067086
Categories: SeismologySolid-earth geophysics
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sketch maps
S47°00'00" - S44°00'00", W78°00'00" - W73°00'00"
Secondary Affiliation: University of Tokyo, JPN, JapanKobe University, JPN, Japan
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Abstract, Copyright, Seismological Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201935
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