33 Mantle Dynamics and Lithospheric Deformation

Wednesday, 27 March 2019
8:00 AM - 12:00 PM
Flint Hills Room

TITLE: STRAIN PARTITIONING ACROSS THE POLOCHIC-MOTAGUA FAULT SYSTEM, GUATEMALA: INSIGHTS FROM KINEMATIC NUMERICAL MODELING

Paper number: 33-3
Program: Theme Sessions
Time: 8:40 AM – 9:00 AM

Authors

Abstract

The Polochic-Motagua Fault System (PMFS) in Guatemala is the on-land segment of the sinistral transform plate boundary between the North American Plate (NA) and the Caribbean Plate (CA). The PMFS has been the locus of major shallow earthquakes over the past 1200 years and assessment of its seismic hazard requires a better understanding of the kinematics of the fault system. GPS monitoring indicates that 75% of the plate motion is accommodated by the Motagua Fault (MF) and 25% by the Polochic Fault (PF). The PF has a documented lateral offset of ~132 ± 5 km and formed a large pull-apart basin that contains more than 4 km of sediment. Previous kinematic models often interpret the PMFS as a singular structure. However, the fault system is complex, comprising two main faults and a multitude of fault branches. The degree of strain partitioning and the connection of the PMFS to the Swan Fault (SF) is poorly documented. This study utilizes 2D Finite Element Analysis (FEA) to generate new kinematic models of the NA and CA relative motion and includes a multitude of faults, as published in geologic maps, to provide a better understanding of strain partitioning across the PMFS. The displacement along different active faults are calibrated with published GPS measurements to obtain a best-fit model. Such models provide a better understanding of the velocity profiles across different faults in the PMFS and help understand which fault is kinematically active and connected to the SF. This modeling approach allows refinement of current structural models to better understand strain partitioning in the PMFS. Such results can aid in future seismic hazard assessment in the area.

Geological Society of America Abstracts with Programs. Vol. 51, No. 2

doi: 10.1130/abs/2019SC-325892

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