24. Advancing Earthquake Response and Crustal Deformation Research with Real-Time Data from the Global Positioning System

During the past two decades it has become routine to produce daily Global Positioning System (GPS) station positions in three dimensions. This system has produced precise estimates of interseismic strain, coseismic displacements for three large earthquakes in southern California (1999 Hector Mine M 7.1, 2003 San Simeon M 6.6, and 2004 Parkfield M 6.0), observations of postseismic transients, and detection of unexpected hydrologic signals (there are many papers on these topics, including scientists from the U.S. Geological Survey (USGS) (USGS and others, 2000; Hudnut and others, 2002a; King and others, 2007). Coseismic displacements were available within hours. While this is a huge improvement over early geodetic systems, it is not fast enough to be useful to emergency responders.

The next big challenge for crustal deformation geodesy is the use of real-time and high-rate rapid geodetic products in crustal deformation research and earthquake response. Southern California, with its large seismic hazard and dense seismic and geodetic arrays, is an excellent laboratory for this work. Advances can be applied anywhere where real-time GPS data exist; these regions now include much of the developed world. Incorporation of rapid geodetic results (displacements, strains, tilts) into ShakeMap and other online products would complement existing seismic results and make GPS an important component of earthquake response. 

Many faults, some within the heavily populated urban area, might cause damaging earthquakes in southern California,. However, only the southern San Andreas fault has the potential for a great earthquake. This fault lies entirely east of the Los Angeles metropolitan area. Depending on the epicenter, the wavefront from such a great earthquake will take about one minute to reach the urban area. Therefore Earthquake Early Warning, the real-time detection of the earthquake and the broadcast of a warning ahead of the seismic wavefront, may be possible for southern San Andreas earthquakes. Current designs use only seismic data. The addition of a “fault slip sensor” based on geodetic data (Hudnut and others, 2002b) would enhance the system by (1) using both seismic and geodetic data to detect an earthquake more robustly, (2) observing displacement directly, and (3) providing observations of surface displacements to constrain finite fault slip models.

The earthquake response component of this Opportunity will be focused on implementation and evaluation of various rapid and real-time GPS processing strategies, development of algorithms to compute strain and tilt fields from GPS displacements, and development of algorithms to discriminate between fault slip and noise in real time. The first two parts will significantly improve USGS' capability to respond to damaging earthquakes. The last goal is by far the most difficult, requiring expertise in signal detection and time series analysis, as well as considerable ingenuity and creativity. Results will indicate whether the fault slip sensor concept can be implemented with current GPS data and processing methods. A positive result would be a “first,” a significant achievement for both the USGS and the Mendenhall Fellow.

The postdoctoral researcher may also explore the application of real-time GPS to other disasters, including landslides, volcanic eruptions (Larson and others, 2001), tsunamis (Dragert and others, 2007; Blewitt and others, 2008), and storms (using the atmospheric results from GPS).

Research topics include, but are not limited to, signal detection methods, error analysis, earthquake strong motion, atmospheric signals related to storms or annual/diurnal cycles, volcanic deformation, landslide detection, rapid earthquake magnitudes for tsunami warning, and the use of seismic and GPS data in finite fault modeling. Just as unexpected signals emerged when daily GPS time series became available more than 10 years ago, data collected at 1-second intervals will doubtless reveal intriguing new signals.

References

Blewitt, G., Kreemer, C., Hammond, B., Plag, H.P., Stein, S., Okal, E., Bar-Sever, Y., Gross, R., Hsu, V., Hudnut, K., Simons, M., Song, T., and Webb, F., 2007, Toward real-time GPS for tsunami warning and post-earthquake damage assessment and emergency response: Paper presented at European Space Agency Workshop, Frascati, Italy.

Dragert, H., Schmidt, M., Wang, K., and Bock, Y., 2007, Towards real-time recognition of near-field tsunamigenic earthquakes: Eos, Transactions of the American Geophysical Union, v. 88, no. 52, Fall Meeting Supplement, Abstract G24A-01.

Hudnut, K.W., King, N.E., Galetzka, J.E., Stark, K.F., Behr, J.A., Aspiotes, A., and Van Wyk, S., 2002a: Continuous GPS observations of postseismic deformation following the 16 October 1999 Hector Mine, California earthquake: Bulletin of the Seismological Society of America, v. 92, p. 1403–1422.

Hudnut, K.W., G.J. Anderson, A.G. Aspiotes, N.E. King, and K.F. Stark, 2002b, GPS fault slip sensors in earthquake alert systems: Eos, Transactions of the American Geophysical Union, v. 83, no. 47, Fall Meeting Supplement, Abstract G52A–0956.

King, N.E., Argus, D., Langbein, J., Agnew, D.C., Bawden, G., Dollar, R.S., Liu, Z., Galloway, D., Reichard, E., Yong, A., Webb, F.H., Bock, Y., Stark, K., and Barseghian, D., 2007, Space geodetic observation of expansion of the San Gabriel valley, California, aquifer system, during heavy rainfall in winter 2004-2005: Journal of Geophysical Research, v. 112, no. B03409, doi:10.1029/2006JB004448.

Larson, K., Cervelli, P., Lisowski, M., Miklius, A., Segall, P., and Owen, S., 2001, Volcano monitoring using the Global Positioning System: Filtering strategies: Journal of Geophysical Research, v. 106, p. 1–12.

Murray, J., King, N., Hudnut, K., Poland, M., Miklius, A., and Lisowski, M., 2007, High-rate, near real-time GPS as a tool for natural hazards mitigation, funded by USGS Venture Capital Program.

U.S. Geological Survey, Southern California Earthquake Center, and California Division of Mines and Geology, 2000, Preliminary report on the 10/16/1999 M7.1 Hector Mine, California earthquake: Seismological Research Letters, v. 71, p. 11–23.

Proposed Duty Station: Pasadena, CA

Areas of Ph.D.: Geophysics, geodesy, seismology

Qualifications: Applicants must meet one of the following qualifications: Research Geologist, Research Geophysicist

(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 the position will be made by the Human Resources specialist.)

Research Advisor(s): Nancy King, (626) 583-7815, nking@usgs.gov; Kenneth Hudnut, (626) 583-7232, hudnut@usgs.gov

Human Resources Office contact: Candace Azevedo, (916) 278-9393, caazevedo@usgs.gov

Summary of Opportunities