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Subduction zone megathrust earthquakes

Susan L. Bilek and Thorne Lay
Subduction zone megathrust earthquakes
Geosphere (Boulder, CO) (August 2018) 14 (4): 1468-1500


Subduction zone megathrust faults host Earth's largest earthquakes, along with multitudes of smaller events that contribute to plate convergence. An understanding of the faulting behavior of megathrusts is central to seismic and tsunami hazard assessment around subduction zone margins. Cumulative sliding displacement across each megathrust, which extends from the trench to the downdip transition to interplate ductile deformation, is accommodated by a combination of rapid stick-slip earthquakes, episodic slow-slip events, and quasi-static creep. Megathrust faults have heterogeneous frictional properties that contribute to earthquake diversity, which is considered here in terms of regional variations in maximum recorded magnitudes, Gutenberg-Richter b values, earthquake productivity, and cumulative seismic moment depth distributions for the major subduction zones. Great earthquakes on megathrusts occur in irregular cycles of interseismic strain accumulation, foreshock activity, main-shock rupture, postseismic slip, viscoelastic relaxation, and fault healing, with all stages now being captured by geophysical monitoring. Observations of depth-dependent radiation characteristics, large earthquake slip distributions, variations in rupture velocities, radiated energy and stress drop, and relationships to aftershock distributions and afterslip are discussed. Seismic sequences for very large events have some degree of regularity within subduction zone segments, but this can be complicated by supercycles of intermittent huge ruptures that traverse segment boundaries. Factors influencing variability of large megathrust ruptures, such as large-scale plate structure and kinematics, presence of sediments and fluids, lower-plate bathymetric roughness, and upper-plate structure, are discussed. The diversity of megathrust failure processes presents a suite of natural hazards, including earthquake shaking, submarine slumping, and tsunami generation. Improved monitoring of the offshore environment is needed to better quantify and mitigate the threats posed by megathrust earthquakes globally.

EISSN: 1553-040X
Serial Title: Geosphere (Boulder, CO)
Serial Volume: 14
Serial Issue: 4
Title: Subduction zone megathrust earthquakes
Affiliation: New Mexico Institute of Mining and Technology, Department of Earth and Environmental Science, Socorro, NM, United States
Pages: 1468-1500
Published: 20180801
Text Language: English
Publisher: Geological Society of America, Boulder, CO, United States
References: 270
Accession Number: 2018-083858
Categories: SeismologySolid-earth geophysics
Document Type: Serial
Bibliographic Level: Analytic
Annotation: Part of Subduction top to bottom 2 themed issue
Illustration Description: illus. incl. 2 tables, geol. sketch maps
Secondary Affiliation: University of California at Santa Cruz, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2018, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201821
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