The relationship between seismicity and fault structure on the Discovery transform fault, East Pacific Rise
Abstract
There is a global seismic moment deficit on mid-ocean ridge transform faults, and the largest earthquakes on these faults do not rupture the full fault area. We explore the influence of physical fault structure, including step-overs in the fault trace, on the seismic behavior of the Discovery transform fault, 4S on the East Pacific Rise. One year of microseismicity recorded during a 2008 ocean bottom seismograph deployment (24,377 0 ML 4.6 earthquakes) and 24 years of Mw 5.4 earthquakes obtained from the Global Centroid Moment Tensor catalog, are correlated with surface fault structure delineated from high-resolution multibeam bathymetry. Each of the 15 5.4 Mw 6.0 earthquakes that occurred on Discovery between 1 January 1990 and 1 April 2014 was relocated into one of five distinct rupture patches using a teleseismic surface wave cross-correlation technique. Microseismicity was relocated using the HypoDD relocation algorithm. The western fault segment of Discovery (DW) is composed of three zones of varying structure and seismic behavior: a zone with no large events and abundant microseismicity, a fully coupled zone with large earthquakes, and a complex zone with multiple fault strands and abundant seismicity. In general, microseismicity is reduced within the patches defined by the large, repeating earthquakes. While the extent of the large rupture patches on DW correlates with physical features in the bathymetry, step-overs in the primary fault trace are not observed at patch boundaries, suggesting along-strike heterogeneity in fault zone properties controls the size and location of the large events. 1.
Department
Center for Coastal and Ocean Mapping
Publication Date
9-29-2014
Volume
15
Journal Title
Geochemistry, Geophysics, Geosystems
Pages
3698-3712
Publisher
American Geophysical Union Publications
Digital Object Identifier (DOI)
10.1002/2014GC005445
Document Type
Journal Article
Recommended Citation
Wolfson-Schwehr, M., M. S. Boettcher, J. J. McGuire, and J. A. Collins (2014), The relationship between seismicity and fault structure on the Discovery transform fault, East Pacific Rise, Geochem. Geophys. Geosyst., 15, 3698– 3712, doi:10.1002/2014GC005445.