30. Exploring the Significance of Earthquake Families for Volcano Monitoring at Mount St. Helens and Other Volcanoes

Over the last two decades volcano seismologists have increasingly recognized the occurrence of “repeating” earthquakes (also known as “earthquake families”). Repeating earthquakes, characterized by nearly identical waveforms, have been seen at a wide variety of volcanoes including Mount St. Helens (Washington), Mount Hood (Oregon), Kilauea (Hawaii), Shishaldin (Alaska), Augustine (Alaska), Mount Unzen (Japan), Soufriére Hills (Montserrat), and Bezymianny (Russia). Studies of these events have focused primarily on exploiting waveform similarity to achieve precise (< 100 meter) relative locations and, more recently, on using temporal variations in the coda of repeating-earthquake sequences to make inferences about temporal changes in structural properties (changes in bulk compressibility, density, temperatures, etc.) near the earthquake source. Although real-time identification of earthquake families has been the focus of recent research in the seismological community, it has yet to be established whether earthquake family identification is critical for near-real-time volcano monitoring and eruption forecasting. One reason for this is that there have been few eruptions with well-constrained eruption-rate histories that have also been accompanied by long-lived, well-recorded earthquake swarms. The 2004-2008 eruption of Mount St. Helens is exceptional in this regard, as it was both well documented and, with over two million earthquakes, highly seismogenic.

This Research Opportunity is targeted at the general issue of the significance of earthquake families to volcano monitoring, as well as to the study of ongoing volcanic processes during eruptive periods. The USGS is responsible for issuing volcanic hazards warnings. The accuracy of such warnings is dependent in part upon research focused on determining the nature of volcanic processes responsible for observed geologic and geophysical phenomena, including volcano seismicity. One goal is to establish whether earthquake families are useful for assessing the likelihood of future eruptive activity, as well as for detecting and accurately forecasting short-term changes in an ongoing eruption. Continuous and well-recorded earthquake datasets exist for the 2004-2008 eruption of Mount St. Helens (MSH) and the 2006 eruption of Augustine Volcano, Alaska. Most of the MSH earthquakes have not been analyzed, and a first-order problem is to determine the earthquake-family chronology through the entire course of the eruption. This has never been done at a volcano on such a scale (two million earthquakes over 3+ years), and by itself would represent a substantial achievement. Once determined, the chronology can be compared to extrusion-rate history, deformation trends, and eruption chronology to assess whether changes in earthquake-family occurrence correlate with changes in eruption dynamics. Identified earthquake families could also be used to determine relative relocations on a massive scale, as well as employing techniques such as coda-wave interferometry to investigate temporal changes in volcanic structure throughout the course of the eruption. This work could easily be extended to other volcanoes, particularly the 2006 eruption of Augustine and other datasets collected by the Alaska Volcano Observatory.

The applicant must have ample experience working with seismological data, be proficient with computer-based data analysis techniques, and preferably have some basic knowledge of volcanology. Experience with cross-correlation analysis, relative relocations, and volcano monitoring is desirable but not required.

Proposed Duty Station: Vancouver, WA

Areas of Ph.D.: Geophysics, seismology, computer science

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

(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): Seth Moran, (360) 993-8934, smoran@usgs.gov; John Power, (907) 786-7426, jpower@usgs.gov; Stephanie Prejean, (907) 786-7462, sprejean@usgs.gov

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

Summary of Opportunities