Woods Hole Oceanographic Institution

Jeffrey J Mcguire

»Gofar Transform Earthquakes

The Network Strain Filter - A New Tool for Monitoring and Detecting Transient Deformation Signals in GPS Arrays


Scaling Relations for Seismic Cycles on Mid-Ocean Ridge Transform Faults

»Earthquake Swarms on Transform Faults
»Modeling Seismic Swarms Triggered by Aseismic Transients
»Analysis of Seafloor Seismograms of the 2003 Tokachi­Oki
  Earthquake Sequence for Earthquake Early Warning

»Seismic Cycles
»Fore-arc structure and subduction zone earthquakes
»Salton Trough Swarms
»Earthquake Predictability
»SEAJADE Experiment

Andrea L. Llenos, Jeffrey J. McGuire, and Yosihiko Ogata , Modeling Seismic Swarms Triggered by Aseismic Transients , submitted to EPSL, 2008

The rate of earthquake occurrence varies by many orders of magnitude in a given region due to variations in the stress state of the crust. Our focus here is on variations in seismicity rate triggered by transient aseismic processes such as fluid flow, fault creep or magma intrusion. While these processes have been shown to trigger earthquakes, converting observed seismicity variations into estimates of stress rate variations has been challenging. Essentially aftershock sequences often obscure changes in the background seismicity rate resulting from aseismic processes. Two common approaches for estimating the time dependence of the underlying driving mechanisms are the stochastic Epidemic Type Aftershock Sequence model (ETAS) (Ogata, 1988) and a physical approach based on the rate- and state-model of fault friction (Dieterich, 1994). The models have different strengths that could be combined to allow more quantitative studies of earthquake triggering. To accomplish this, we identify the parameters that relate to one another in the two models and examine their dependence on stressing rate. A particular conflict arises because the rate-state model predicts that aftershock productivity scales with stressing rate while the ETAS model assumes that it is time independent. To resolve this issue, we estimate triggering parameters for 4 earthquake swarms contemporaneous with geodetically observed deformation transients in various tectonic environments. We find that stressing rate transients increase the background seismicity rate without affecting aftershock productivity. We then specify a combined model for seismicity rate variations that will allow future studies to invert seismicity catalogs for variations in aseismic stressing rates.

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