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- Title
Earthquake Magnitude Distributions on Northern Caribbean Faults From Combinatorial Optimization Models.
- Authors
Geist, Eric L.; ten Brink, Uri S.
- Abstract
On‐fault earthquake magnitude distributions are calculated for northern Caribbean faults using estimates of fault slip and regional seismicity parameters. Integer programming, a combinatorial optimization method, is used to determine the optimal spatial arrangement of earthquakes sampled from a truncated Gutenberg‐Richter distribution that minimizes the global misfit in slip rates on a complex fault system. Slip rates and their uncertainty on major faults are derived from a previously published GPS block model for the region, with fault traces determined from offshore geophysical mapping and previously published onshore studies. The optimal spatial arrangement of the sampled earthquakes is compared with the 500‐year history of earthquake observations. Rupture segmentation of the subduction interface along the Hispaniola‐Puerto Rico Trench (PRT) fault and seismic coupling on the PRT fault appear to exert the primary control over this spatial arrangement. Introducing a rupture barrier for the Hispaniola‐PRT fault northwest of Mona Passage, based on geophysical and seismicity observations, and assigning a low slip rate of 2 mm/yr on the PRT fault are most consistent with historical earthquakes in the region. The addition of low slip‐rate secondary faults as well as segmentation of the Hispaniola and Septentrional strike‐slip fault improves the consistency with historical seismicity. An important observation from the modeling is that varying the slip rate on the PRT fault and different segmentation scenarios result in significant changes to the optimal magnitude distribution on faults farther away. In general, optimal on‐fault magnitude distributions are more complex and inter‐dependent than is typically assumed in probabilistic seismic hazard analysis and probabilistic tsunami hazard analysis. Plain Language Summary: High population density and unreinforced structures make the northern Caribbean region especially susceptible to earthquakes. The region's complex fault system includes a major offshore fault north of Hispaniola and Puerto Rico separating two tectonic plates, as well as several major crustal faults crossing the islands. During the region's 500‐year recorded history, major earthquakes and tsunamis, including the devastating 2010 and 2021 earthquakes in Haiti, resulted from movement along these faults. The range of magnitudes for each fault is critical in assessing earthquake hazard throughout the region. In this study, we employ a novel method, integer programming, from the disparate field of operations research to determine the optimal distribution of large earthquakes on the northern Caribbean fault system. Rather than assessing each fault independently, the distribution of earthquakes under various scenarios is determined for the system as a whole, with specific assumptions regarding fault geometry and slip rate on one fault affecting the forecasted magnitudes on other faults. We find that segmentation of major faults increases the frequency earthquakes in the range of magnitude 6.0–7.0. In addition, the magnitude of the largest earthquakes occurring on the offshore plate boundary faults may be significantly less than previously assumed for tsunami hazard assessments. Key Points: On‐fault earthquake magnitude distributions for northern Caribbean faults are calculated using the integer programming methodHistorical earthquakes, including the 2010 and 2021 Haiti earthquakes, are used to evaluate scenarios of fault segmentation and couplingFault characterization assumptions on one fault influence earthquake magnitude distributions on other faults farther away
- Subjects
EARTHQUAKE magnitude; EARTHQUAKES; SEISMOLOGY; EARTH movements; PLATE tectonics; GLOBAL Positioning System
- Publication
Journal of Geophysical Research. Solid Earth, 2021, Vol 126, Issue 10, p1
- ISSN
2169-9313
- Publication type
Article
- DOI
10.1029/2021JB022050