Seismogenic Cutoff Depths and Thermal State of the Late-Interseismic Central Alpine Fault, New Zealand: Implications for Coseismic Slip in Future Large Earthquakes
Session: Exploring Rupture Dynamics and Seismic Wave Propagation Along Complex Fault Systems [Poster]
Type: Poster
Date: 4/19/2021
Presentation Time: 03:45 PM Pacific
Description:
Observations made during last decade of microseismicity near the central section of the Alpine Fault reveal marked along-strike variations in seismogenic cutoff depths late in the fault’s <300-year interseismic period. We use the entire microseismicity catalog (~7700 events) in conjunction with thermochronological data to estimate the rates and thermal effects of ongoing exhumation of the Southern Alps orogen, which forms the hanging-wall of the Alpine Fault. We obtain uplift rates of between 1 and 8 mm/yr, with maximum values coinciding with the area of highest topography near Aoraki/Mount Cook: these estimates compare well with recent geodetic measurements and with independent thermochronological data not used in our modeling. The mean brittle-ductile transition temperature beneath the Southern Alps we obtain (410–430°C) is higher than expected for a quartz-dominated rheology, and may reflect unmodeled effects of elevated fluid pressures or strain rate heterogeneity. The variation in seismogenic cutoff depths along strike of the Alpine Fault is well accounted for by the temperature structure and likely affects both down-dip and along-strike patterns of coseismic slip in large Alpine Fault earthquakes. Using all events in the microseismicity catalog as templates, we are now undertaking a comprehensive matched-filter analysis in order to detect additional lower-magnitude seismicity and explore spatial variations in moment release and susceptibility to triggering by regional earthquakes. In this presentation we discuss the ramifications of the seismological and thermal results for the distribution of coseismic slip and outline methods by which these findings are being incorporated in virtual earthquake models of future earthquakes.
Presenting Author: John Townend
Student Presenter: No
Authors
John Townend Presenting Author Corresponding Author john.townend@vuw.ac.nz Victoria University of Wellington |
Konstantinos Michailos konstantinos.michailos@unil.ch University of Lausanne |
Rupert Sutherland rupert.sutherland@vuw.ac.nz Victoria University of Wellington |
Martha Savage martha.savage@vuw.ac.nz Victoria University of Wellington |
Calum Chamberlain calum.chamberlain@vuw.ac.nz Victoria University of Wellington |
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Seismogenic Cutoff Depths and Thermal State of the Late-Interseismic Central Alpine Fault, New Zealand: Implications for Coseismic Slip in Future Large Earthquakes
Category
Exploring Rupture Dynamics and Seismic Wave Propagation Along Complex Fault Systems