Thesis
Geodetic solutions of global earthquakes with InSAR: August 2019-August 2020
University of Iowa
Master of Science (MS), University of Iowa
Summer 2021
DOI: 10.17077/etd.005783
Abstract
When an earthquake occurs, hazard response operations are reliant on seismic catalogssuch as the ANSS/USGS Comprehensive Catalog (USGS) and Global Centroid Moment Tensor (Global CMT) to provide information about the causative fault. Interferometric Synthetic Aperture Radar (InSAR) is a satellite measurement that can be used to supplement seismic catalogs. The Geodetic Centroid (gCent) Project began in August 2019 and used InSAR to monitor global earthquakes. The purpose of gCent is to systematically document earthquakes with InSAR and to generate an InSAR-derived earthquake catalog. Out of 65 events processed, 28 were successfully imaged and modeled. After obtaining imagery of the surface deformation, I created finite fault models that best replicate the displacement measured by InSAR. My models provide the fault’s orientation (strike, dip), location (latitude, longitude, depth), and the magnitude of slip (slip, rake). I compare two earthquake catalogs, the USGS/ANSS Comprehensive Catalog (USGS) and Global Centroid Moment Tensor (Global CMT) catalog, to the gCent catalog in an effort to identify systematic differences and similarities between geodetically and seismically-calibrated earthquake catalogs. I find that gCent is closer to Global CMT for strike, dip, and rake. However, gCent is more similar to USGS for the earthquake location (centroid, or the center of the fault plane for gCent, and epicenter for USGS). Moment magnitude (Mw) is the same average between both comparisons. Additionally, I add my fault dimensions results to previously published geodetically-derived fault scaling relationships. My solutions tend to produce larger fault areas for the Mw, but my earthquake scaling relationships are in agreement with previous studies. This project highlights the similarities and variances between seismic and geodetic data for earthquake science and the increasing importance of InSAR in earthquake studies.
Details
- Title: Subtitle
- Geodetic solutions of global earthquakes with InSAR: August 2019-August 2020
- Creators
- Hannah Nicole Shea
- Contributors
- William D Barnhart (Advisor)David W Peate (Committee Member)Mark K Reagan (Committee Member)
- Resource Type
- Thesis
- Degree Awarded
- Master of Science (MS), University of Iowa
- Degree in
- Geoscience
- Date degree season
- Summer 2021
- DOI
- 10.17077/etd.005783
- Publisher
- University of Iowa
- Number of pages
- viii, 39 pages
- Copyright
- Copyright 2021 Hannah Nicole Shea
- Language
- English
- Description illustrations
- color illustrations, color maps
- Description bibliographic
- Includes bibliographical references (pages 16-21).
- Public Abstract (ETD)
As soon as an earthquake happens, scientists assess the event by gathering data and creating models to describe the fault. Global hazard response operations rely on these models to understand the earthquake mechanisms. Earthquake catalogs are a thorough summary of the fault that caused the event and include information about the earthquake such as: the fault’s orientation, earthquake location, and earthquake magnitude. Two of these earthquake catalogs are the USGS/ANSS Comprehensive Catalog (USGS) and Global Centroid Moment Tensor (Global CMT). These catalogs are created using seismic data. Another way to describe the fault is through Interferometric Synthetic Aperture Radar (InSAR). InSAR measures the ground surface and detects deformation caused by the earthquake. By measuring this ground displacement, fault models below the Earth’s surface can be used to imitate the surface deformation to estimate the fault’s parameters. These models can be used to create an InSAR earthquake catalog. Over the span of a year, the Geodetic Centroid (gCent) Project imaged 28 earthquakes out of a potential 65 using a specific criteria. I modeled these events to create a gCent earthquake catalog containing the fault’s orientation (strike, dip rake), earthquake location (latitude, longitude, depth), and slip characteristics (rake, slip magnitude). These fault models were used for the hazard application USGS ShakeMap. This catalog is also compared to well-known earthquake catalogs USGS and Global CMT to determine if there are consistent differences between the earthquake solutions. I find that Global CMT is more similar to the gCent catalog with the fault’s strike, dip, and rake. I also conclude that USGS epicenters are more similar to gCent centroids, or the center of average moment release (for this study, the center of the fault plane). Moment magnitude (Mw) is the same between both catalogs. I discuss scaling relationships (Fault area (A) and Mw) to previous studies and I find that, although I consistently overestimate the fault’s area to Mw, the scaling relationships are similar to what has been previously analyzed. This project validates the importance of recognizing consistent differences between gCent and the other seismic catalogs, USGS and Global CMT, and demonstrates the use of InSAR in earthquake studies.
- Academic Unit
- Earth and Environmental Sciences
- Record Identifier
- 9984124269402771
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