14-31. Improving Earthquake Location Procedures Using Calibration Events and Signal Processing. Significantly Advancing our Understanding of Earthquake Sequences and Seismotectonics
We seek a Mendenhall Fellow to conduct research on using innovative earthquake detection and location methods to significantly improve the accuracy of global earthquake locations used in a wide variety of earth science emergency response and solid earth science research applications. An earthquake location is a 1st order parameter used in mission-critical emergency response activities at the USGS National Earthquake Information Center (NEIC). After significant global and domestic events, earthquake locations are released to the public within approximately 20 minutes of event occurrence, and updated over the following days and weeks as new data become available. The final catalog of earthquake locations and magnitudes is the basis on which the Earth science community conducts long-term hazards assessment. Accurate near-real-time earthquake locations are also critical in estimating shaking and impact during the minutes and hours following a damaging earthquake.
Today, earthquake locations are principally derived with essentially the same methods that were proposed approximately 100 years ago by Geiger – to locate seismic events one-at-a-time using phase picks and a theoretical model of travel times. While the way we approach this problem has evolved slightly, becoming more sophisticated and more accurate as more data have been collected, the underlying principles remain the same. More recently, a variety of approaches to earthquake relocation (e.g., Joint Hypocentral Determination, Dewey, 1972; Hypocentral Decomposition, Jordan and Sverdrup, 1981; Double Difference, Waldhauser and Ellsworth, 2000; correlation-based re-picking and relocation, Aster et al., 2000) have shown that using information from multiple events simultaneously allows significant improvements to both absolute and relative earthquake locations, reducing regional-scale location uncertainties from the kilometers to tens of kilometers scale to perhaps as low as several hundred meters. However, these approaches have not yet been systematically adapted for and applied to teleseismic location problems at the USGS as part of our global real-time monitoring responsibilities (or otherwise, with historic catalogs and data). It is likely that existing approaches to the earthquake relocation problem will require some adaptation to deal with data on global scales, in comparison to the local and regional scale problems to which these techniques are usually applied.
Such improvements can provide remarkable new insights into earthquake shaking and seismic hazard. These more complete and accurate new catalogs also allow researchers to better elucidate the details of earthquake distributions and the seismotectonic framework of seismically active areas of the world, as well as to advance research in basic earthquake phenomenology and physics. The processing and storage requirements for rapidly running such procedures are now achievable. Consequently, it is imperative to explore their adaptation for and integration into NEIC's earthquake monitoring and cataloging system, and their use in longer-term research applications that include Operational Earthquake Forecasting, Earthquake Early Warning, Impact Assessment and State-of-the-Art Earthquake Hazards Assessment.
Many approaches to improvements in earthquake location exist already using research-based techniques, and we do not wish to repeat the detailed work represented by those studies. Instead, we seek candidates who can demonstrate how to systematically and consistently adopt the use of these novel methods for global-scale problems, taking advantage of well-calibrated seismicity catalogs in some seismically active areas of the world, and benefitting from the accessibility to large quantities of waveform data, processing power, and database capabilities at NEIC. Specifically, much research is needed to demonstrate the applicability of earthquake relocation procedures in regions where seismicity and data coverage are more widely distributed than typically available when using local/regional earthquake catalogs and network data. This may require building upon and improving existing methodologies. Similarly, the adoption of these techniques for near real-time location procedures will require significant research into a variety of algorithms, their relative benefits, and their optimization for the delivery of rapid and accurate earthquake locations.
By working on new approaches to improve NEIC earthquake location algorithms for both regionally and teleseismically recorded earthquakes, the successful candidate will be directly improving USGS, and US and global seismological community, capabilities to rapidly characterize earthquakes and their potential effects and will help to improve the standards of our future and historic earthquake catalogs. In turn, these issues will facilitate better estimations of shaking after an earthquake, improved analyses of stress changes relevant to aftershock and triggering probabilities, and in the long term will also facilitate improved understanding of earthquake processes. This work also directly relates to one of the U.S. National Science Foundation’s Grand Challenges in Seismology (Lay et al., 2009), where it was specifically noted that improvements in the accuracy of event locations on global scales are feasible, and would benefit not just basic and applied research, but also other societal applications dependent on seismicity distributions (for example, seismic hazard maps and PAGER impact assessments).
We invite proposals from candidates with experience in regional or global seismology, geophysics, and/or seismic wave propagation, and with specific interest and/or experience in earthquake location and waveform cross-correlation. The successful candidate will explore the opportunistic use of a complete suite of NEIC and community datasets (e.g., permanent and temporary regional, and teleseismic datasets, and using phase picks and/or full waveform information) and earthquake location/relocation techniques, with an ultimate goal of significantly improving location algorithms and historic earthquake catalogs used and maintained by the USGS/NEIC for broad public and scientific benefit.
Aster, R., and Rowe, C., 2000. Automatic phase pick refinement and similar event association in large seismic datasets, in: Thurber, C., Kissling, E, Rabinowicz, N., eds., Advances in Seismic Event Location 18, Kluwer Academic Publishers, Dordrecht.
Dewey, J.W., 1972. Seismicity and tectonics of western Venezuela, Bull. Seis. Soc. Am.62, 1711-1751.
Jordan, T.H., and Sverdrup, K.A., 1981. Teleseismic location techniques and their application to earthquake clusters in the South-Central Pacific, Bull. Seis. Soc. Am.71, 1105-1130.
Lay, T., ed., 2009. Seismological Grand Challenges in Understanding Earth’s Dynamic Systems. Report to the National Science Foundation, IRIS Consortium, 76pp.
Waldhauser, F., and Ellsworth, W.L., 2000. A double-difference earthquake location algorithm: method and application to the northern Hayward fault, California, Bull. Seismol. Soc. Am., 90, 1353–1368.
Proposed Duty Station: Golden, CO
Areas of Ph.D.: Geophysics, seismology or related fields (candidates holding a Ph.D. in other disciplines but with knowledge and skills relevant to the Research Opportunity may be considered).
Qualifications: Applicant must meet one of the following qualifications - Research Geologist, Research Geophysicist, Computer Scientist, Research Physicist, Research Mathematician.
(This type of research is performed by those who have backgrounds for the occupations stated above. However, other titles may be applicable depending on the applicant’s background, education, and research proposal. The final classification of theposition will be made by the Human Resources specialist).
Research Advisor(s): Harley Benz, (303) 273-3902, email@example.com; Paul Earle, (303) 273-8417, firstname.lastname@example.org; Gavin Hayes, (303) 273-8421, email@example.com; Daniel McNamara, (303) 273-8550, firstname.lastname@example.org; Steve Myers (Lawrence Livermore National Laboratory, Livermore, CA), (925) 423-4988, email@example.com; Rick Aster (Colorado State U), (970) 491-5661, Rick.Aster@colostate.edu.; and Keith Koper (University of Utah, Salt Lake City, UT), (801) 581-6274, firstname.lastname@example.org
Human Resources Office Contact: Robert Hosinski, (916) 278-9397, email@example.com
|Summary of Opportunities|