HR: 1330h
AN: B12A-0745    [PDF]
TI: Spatial and Temporal Variability in Seismicity of the East Pacific Rise: Constraints from Hydroacoustic Monitoring and Evidence for Triggering of Transform Earthquakes
AU: * Gregg, P M
EM: trish@whoi.edu
AF: MIT-WHOI Joint Program, Dept. of Geology and Geophysics, MS 24 Woods Hole Oceanographic Institution, Woods Hole, MA 02543
AU: Smith, D K
EM: dsmith@whoi.edu
AF: Woods Hole Oceanographic Institution, Dept. of Geology and Geophysics, MS 22 Woods Hole Oceanographic Institution, Woods Hole, MA 02543
AU: Lin, J
EM: jlin@whoi.edu
AF: Woods Hole Oceanographic Institution, Dept. of Geology and Geophysics, MS 22 Woods Hole Oceanographic Institution, Woods Hole, MA 02543
AB: We utilize hydroacoustic data collected since May 1996 by NOAA's Equatorial Pacific autonomous hydrophone array to investigate the first order spatial and temporal variability of seismicity at the East Pacific Rise (EPR) within the array. We also investigate earthquake stress interaction and triggering at three sites: the Clipperton and Siqueirous transform faults, which are part of the Ridge2000 EPR Integrated Study Site (ISS), as well as a section of the ridge at $5.4\deg$S near the Gofar transform fault. Our analyses reveal strong evidence of seismic clustering along the EPR. The majority of earthquakes ($>90%$) clustered in seismic swarms, in which individual events occurred within a few km and within minutes or hours of each other. Through correlating hydrophone data to teleseismically recorded events, we have located several moderate size earthquakes on the Siqueiros and Clipperton transforms. Some of these moderate size events occurred closely in space and time, suggesting the possibility of earthquake triggering. At $5.4\deg$S we found evidence for possible interaction between two moderate size events, one of which occurred on the EPR axis and the other about 100 km northward on the Gofar transform fault. Stress calculations were carried out for several pairs of the moderate size events. The close correlation of the calculated Coulomb stress changes with the observed spatial and temporal variations in seismicity patterns provide strong evidence for possible earthquake triggering along the transform faults. This might have important implications for processes acting in the EPR ISS, including the relationship between seismicity and changes in hydrothermal circulation patterns.
DE: 0935 Seismic methods (3025)
DE: 3035 Midocean ridge processes
SC: Biogeosciences [B]
MN: 2003 Fall Meeting