Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published April 2022 | Supplemental Material + Published
Journal Article Open

Very Low Frequency Earthquakes in Between the Seismogenic and Tremor Zones in Cascadia?


Megathrust earthquakes and their associated tsunamis cause some of the worst natural disasters. In addition to earthquakes, a wide range of slip behaviors are present at subduction zones, including slow earthquakes that span multiple orders of spatial and temporal scales. Understanding these events may shed light on the stress or strength conditions of the megathrust fault. Out of all types of slow earthquakes, very low frequency earthquakes (VLFEs) are most enigmatic because they are difficult to detect reliably, and the physical nature of VLFEs are poorly understood. Here we show three VLFEs in Cascadia that were dynamically triggered by a 2009 Mw 6.9 Canal de Ballenas earthquake in the Gulf of California. The VLFEs likely locate in between the seismogenic zone and the Cascadia episodic tremor and slip (ETS) zone, including one event with a moment magnitude of 5.7. This is the largest VLFE reported to date, causing clear geodetic signals. Our results show that the Cascadia megathrust fault might slip rapidly at some spots in this gap zone, and such a permissible slip behavior has direct seismic hazard implications for coastal communities and perhaps further inland. Further, the observed seismic sources may represent a new class of slip events, whose characteristics do not fit current understandings of slow or regular earthquakes.

Additional Information

© 2022. The Authors. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made. Issue Online: 11 March 2022; Version of Record online: 11 March 2022; Accepted manuscript online: 08 March 2022; Manuscript accepted: 04 February 2022; Manuscript revised: 03 February 2022; Manuscript received: 29 October 2021. We thank David Shelly, Joan Gomberg, Kelin Wang, the three anonymous reviewers, and the editor Thorsten Becker for thoughtful, constructive comments that led to significant improvements to this manuscript. W. Fan was supported by NSF EAR-2143413. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. IRIS Data Services are funded through the Seismological Facilities for the Advancement of Geoscience and EarthScope (SAGE) Proposal of the National Science Foundation (NSF) under Cooperative Agreement EAR-1261681. High-frequency strain data from the Network of the Americas (NOTA) network were also obtained from the IRIS DMC; this material is based on services provided by the Geodesy Advancing Geosciences and EarthScope (GAGE) facility, operated by UNAVCO, Inc., with support from the NSF and the National Aeronautics and Space Administration (NASA) under NSF Cooperative Agreement EAR-1724794. Data Availability Statement: The seismic data were provided by Data Management Center (DMC) of the Incorporated Research Institutions for Seismology (IRIS). The facilities of IRIS Data Services, and specifically the IRIS Data Management Center, were used for access to waveforms, related metadata, and/or derived products used in this study. NOTA Level 2 strain and GNSS data were obtained from UNAVCO web-services (https://www.unavco.org/data/web-services/web-services.html). The tremor catalog is obtained from the Pacific Northwest Seismic Network and the World Tremor Database (http://www-solid.eps.s.u-tokyo.ac.jp/∼idehara/wtd0/Welcome.html). The earthquake catalogs used in this study are from the Global Centroid Moment Tensor project (GCMT) (Ekström et al., 2012).

Attached Files

Published - AGU_Advances_-_2022_-_Fan_-_Very_Low_Frequency_Earthquakes_in_Between_the_Seismogenic_and_Tremor_Zones_in_Cascadia.pdf

Supplemental Material - 2021av000607-sup-0001-supporting_information_si-s01.pdf

Supplemental Material - 2021av000607-sup-0002-original_version_of_manuscript-s01.pdf

Supplemental Material - 2021av000607-sup-0003-peer_review_history-s02.pdf

Supplemental Material - 2021av000607-sup-0004-first_revision_of_manuscript__accepted_-s03.pdf

Supplemental Material - 2021av000607-sup-0005-authors_response_to_peer_review_comments-s04.pdf



Additional details

August 22, 2023
October 23, 2023