Fault Architecture of the Westmost Gofar Transform Fault, East Pacific Rise
Oceanic transform faults (OTFs) are apparently simple tectonic plate boundaries. However, their structures are surprisingly complex as manifested through various seismic and aseismic slip modes. Here we use ocean-bottom-seismometer data collected during a 2008 marine experiment to study the westmost Gofar transform fault. The dataset records the end and early stages of a M6 earthquake seismic cycle and offers a unique opportunity to investigate the fault architecture, seismicity evolution and their inter-relations in regulating earthquake rupture processes. We identify multiple segments along the Gofar fault that have distinct seismic behaviors. In addition to previously identified locked and barrier zones, we find the segment connecting to the East Pacific Rise is characterized by quasi-periodic swam activities. Particularly, this segment hosted a 2-week long swam in December 2008 showing a clear eastward migration and breaking a newly identified shallow fault patch. In between this swarm segment and the 2008 M6 mainshock zone, seismicity is influenced by both the mainshock and the December swarm. Previous studies show that the barrier zone east of the mainshock zone hosted abundant foreshocks preceding the M6 event and halted its active seismicity afterwards. Our new analyses show that the barrier zone has two layers of earthquakes that responded to the M6 earthquake differently. Our results suggest highly heterogenous fault architectures along strike, and fault patches interact and trigger each other over a broad temporal scale. It is unclear how such heterogenous structures were developed at this geologically simple region, but we speculate that the fault architecture variations result from complex fault geometry, fluid-rock interactions and transient tectonic events. Our findings generally agree with the multimode-slip-partitioning mechanisms of OTFs, but also deviate from the synoptic view, highlighting complex internal fault structures at multiple scales.
Session: Frontiers in Marine Seismology [Poster]
Type: Poster
Room: Evergreen Ballroom
Date: 4/22/2022
Presentation Time: 08:00 AM Pacific
Presenting Author: Jianhua Gong
Student Presenter: No
Additional Authors
Jianhua Gong Presenting Author Corresponding Author j4gong@ucsd.edu Scripps Institution of Oceanography, University of California, San Diego |
Wenyuan Fan wenyuanfan@ucsd.edu Scripps Institution of Oceanography, University of California, San Diego |
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Fault Architecture of the Westmost Gofar Transform Fault, East Pacific Rise
Category
Frontiers in Marine Seismology
Description