Relative Seismic Event Location and Size Estimation, Contributions to Earthquake Analysis and Seismic Discrimination at Local Distances
Open Access
- Author:
- Kintner, Jonas
- Graduate Program:
- Geosciences
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- June 07, 2019
- Committee Members:
- Charles James Ammon, Dissertation Advisor/Co-Advisor
Charles James Ammon, Committee Chair/Co-Chair
Andrew Arnold Nyblade, Committee Member
Christelle Wauthier, Committee Member
Parisa Shokouhi, Outside Member - Keywords:
- Geophysics
Seismology
Iran
Caribbean
Pennsylvania
Wyoming - Abstract:
- Improving estimates of seismic source parameters is fundamental for understanding earthquake processes and enhancing current seismic event monitoring capabilities. In this dissertation I address several scientific challenges regarding the characterization (location, magnitude, etc.) of seismic events. Better source characterization allows us to relate seismic activity to observed surface deformation and to the broader tectonic implications of hazardous earthquakes. From a seismological perspective, I extend recently-developed surface-wave based methods to characterize seismic events across a wider range of tectonic environments, event sizes, station distributions, noise environments, and seismic source types. The first study documented is focused on constraining the relative locations and sizes of moderate-magnitude earthquakes in the 2013-2014 Minab sequence, Iran. We combined surface-wave cross correlation measurements, surface-wave spectra, and teleseismic body-wave modeling to constrain epicentroid locations, magnitudes, and depths. The results show that at least in some cases, we can use distant observations to improve the precision of relative earthquake epicentroid locations and magnitudes of remote earthquake sequences in tectonically complex regions. An appendix documents the results from relative relocations across the broad region including and surrounding Iran. Also included is a study of the 2014-15 Bushkan earthquake sequence, Iran. For this moderate-magnitude, shallow event, we used a combination of surface wave analysis, body wave modeling, and InSAR observations to characterize the mainshock and larger aftershocks. This study illuminates the opportunities provided by joint analysis of geodetic and seismological observations from modest-magnitude, shallow earthquakes in remote regions. Next I describe a study in which we characterize earthquake activity along the northwestern Caribbean plate boundary. We analyzed the earthquake processes along this margin by computing precise relative locations and magnitudes of moderate sized earthquakes from 1976 to 2018, and comparing the source-time functions and finite-fault models of the two largest recent earthquakes in the region. The relocation analysis allows us to improve relative event locations that help define the seismically active portions of the plate boundary more clearly. The finite-fault rupture models suggest that the large earthquakes along this strike-slip system may be influenced by faulting asperities and/or restraining bend features. The fourth study is an extension of the relative event location and magnitude estimation methods used in previous analyses. We estimate precise relative locations and magnitudes of small industrial explosions across Pennsylvania, USA using local and near-regional short-period shear-wave observations. The analysis is an effective illustration of the use of cross correlation of local-distance observations to compute high precision relative location and magnitude estimates of low-yield seismic sources. The final analysis described is an investigation of the potential to discriminate between earthquakes, mine blasts, and single shot borehole explosions using the amplitude ratio between local-distance (<200 km) short period surface waves (Rg) and crustal shear wave (Sg) signals in the Bighorn region, Wyoming. We expand current discrimination methods by fitting the observations to a simple model that allows us to quantify geometrical spreading/attenuation and site amplification factors. The results suggest that the Rg/Sg discriminant works in the Bighorn region, but may be sensitive to explosion emplacement conditions, source size, and possibly source depth.