Characterization of Swarm and Mainshock–Aftershock Behavior in Puerto Rico

Author:

Ventura-Valentín Wilnelly1,Brudzinski Michael R.1ORCID

Affiliation:

1. Department of Geology and Environmental Earth Science, Miami University, Oxford, Ohio, U.S.A.

Abstract

Abstract The recent Indios, Puerto Rico earthquake sequence has drawn attention, as the increased seismicity rate in this area was unprecedented. The sequence began on 28 December 2019, caused a 6.4 magnitude earthquake on 7 January 2020, and remained active over a year later. This sequence fits the nominal definition of an earthquake swarm in that it had an abrupt onset, a sustained high rate of seismicity without a clear triggering mainshock or evidence for Omori decay, and a lack of adherence to Bath’s law. However, the sequence also had several prominent mainshock–aftershock (MS–AS) sequences embedded within it. We applied three-station waveform cross correlation to the early part of this sequence using the Puerto Rico Seismic Network (PRSN) catalog as templates, which confirmed the mixture of swarm and MS–AS patterns. In an effort to place this intriguing sequence in the context of the previous seismicity in Puerto Rico, we investigated the existence of swarms and MS–AS sequences recorded by the PRSN since 1987 by identifying sequences with increased seismicity rate when compared to the background rate. About 59 sequences were manually verified and characterized into swarms or MS–AS. We found that 58% of the sequences follow traditional swarm patterns and 14% adhere to traditional MS–AS behavior, whereas 29% of the sequences have a mixture of both swarm and MS–AS behaviors. These findings suggest that it is not unusual for the Indios sequence to have a mixture of both the characteristics. In addition, the detection of many swarms distributed over a broad area of the subduction interface indicates stress heterogeneity and low-coupling consistent with prior studies indicating that the potential for a magnitude ∼8 megathrust earthquake along the Puerto Rico trench is unlikely.

Publisher

Seismological Society of America (SSA)

Subject

Geophysics

Cited by 3 articles. 订阅此论文施引文献 订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献

1. Aftershock Forecasting;Annual Review of Earth and Planetary Sciences;2023-10-12

2. A Detailed View of the 2020–2023 Southwestern Puerto Rico Seismic Sequence with Deep Learning;Bulletin of the Seismological Society of America;2023-07-06

3. Preface to the SRL Focus Section on the 2020 Southwestern Puerto Rico Mw 6.4 Earthquake and Seismic Sequence;Seismological Research Letters;2022-02-09

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