Presentation Title

Imaging Seismicity in the Izu-Bonin-Marianas Subduction Zone

Faculty Mentor

Jascha Polet

Start Date

18-11-2017 2:15 PM

End Date

18-11-2017 3:15 PM

Location

BSC-Ursa Minor 23

Session

Poster 3

Type of Presentation

Poster

Subject Area

physical_mathematical_sciences

Abstract

We present our results of waveform analysis for determining the depths of intermediate-depth earthquakes within the Izu-Bonin-Marianas (IBM) subduction zone. This 2800 km tectonic-plate convergent boundary is the result of the Pacific Plate subducting beneath the Philippines Plate. Improved imaging of the earthquake locations will enhance our knowledge of the mechanisms that generate these IBM events within the subducting slab. The Global Centroid Moment Tensor (GCMT) project automatically determines depths of earthquakes that occur globally. However, these depths are typically not very well constrained, so we are applying waveform modeling to obtain more accurate depths. We have created synthetic seismograms for P-waves at global stations, for a range of depths, where the best-fit matches with a corresponding recorded seismogram will provide accurate depths. Waveforms for 40 seismic events were collected from the Incorporated Research Institutions for Seismology website. Events were selected for a time period between 1990 and 2016, a location within the range 11N - 34N and 134E - 147E, and a minimum magnitude of 5.5. The seismometers that provided the data were selected to have a favorable azimuthal coverage from the IBM subduction zone, with an epicentral distance between 30 and 90 degrees, to avoid any P-wave complications. We are analyzing the occurrence of these earthquakes using seismogram comparisons and will plot the final locations in cross-sections to more accurately determine the depth range over which the subducting slab in the Pacific Plate is seismically inactive. Finally, we will relate these observations to models of deep seismogenesis. For a subset of these earthquakes, preliminary results show a tendency for the depths determined with waveform analysis to be deeper than those generated by GCMT. We are currently developing strategies to address issues related to the relatively low signal-to-noise ratio of the depth phases in some of our waveforms.

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Nov 18th, 2:15 PM Nov 18th, 3:15 PM

Imaging Seismicity in the Izu-Bonin-Marianas Subduction Zone

BSC-Ursa Minor 23

We present our results of waveform analysis for determining the depths of intermediate-depth earthquakes within the Izu-Bonin-Marianas (IBM) subduction zone. This 2800 km tectonic-plate convergent boundary is the result of the Pacific Plate subducting beneath the Philippines Plate. Improved imaging of the earthquake locations will enhance our knowledge of the mechanisms that generate these IBM events within the subducting slab. The Global Centroid Moment Tensor (GCMT) project automatically determines depths of earthquakes that occur globally. However, these depths are typically not very well constrained, so we are applying waveform modeling to obtain more accurate depths. We have created synthetic seismograms for P-waves at global stations, for a range of depths, where the best-fit matches with a corresponding recorded seismogram will provide accurate depths. Waveforms for 40 seismic events were collected from the Incorporated Research Institutions for Seismology website. Events were selected for a time period between 1990 and 2016, a location within the range 11N - 34N and 134E - 147E, and a minimum magnitude of 5.5. The seismometers that provided the data were selected to have a favorable azimuthal coverage from the IBM subduction zone, with an epicentral distance between 30 and 90 degrees, to avoid any P-wave complications. We are analyzing the occurrence of these earthquakes using seismogram comparisons and will plot the final locations in cross-sections to more accurately determine the depth range over which the subducting slab in the Pacific Plate is seismically inactive. Finally, we will relate these observations to models of deep seismogenesis. For a subset of these earthquakes, preliminary results show a tendency for the depths determined with waveform analysis to be deeper than those generated by GCMT. We are currently developing strategies to address issues related to the relatively low signal-to-noise ratio of the depth phases in some of our waveforms.