HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Figures Only Full Text Full Text (PDF) Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (9) Citing Articles via Google Scholar Google Scholar Articles by Moran, S. C. Search for Related Content GeoRef GeoRef Citation

Multiple Seismogenic Processes for High-Frequency Earthquakes at Katmai National Park, Alaska: Evidence from Stress Tensor Inversions of Fault-Plane Solutions

Seth C. Moran
U.S. Geological Survey
Alaska Volcano Observatory
4200 University Dr.
Anchorage, Alaska 99508
scmoran{at}usgs.gov

Manuscript received 25 April 2002.

The volcanological significance of seismicity within Katmai National Park has been debated since the first seismograph was installed in 1963, in part because Katmai seismicity consists almost entirely of high-frequency earthquakes that can be caused by a wide range of processes. I investigate this issue by determining 140 well-constrained first-motion fault-plane solutions for shallow (depth < 9 km) earthquakes occurring between 1995 and 2001 and inverting these solutions for the stress tensor in different regions within the park. Earthquakes removed by several kilometers from the volcanic axis occur in a stress field characterized by horizontally oriented ₁ and ₃ axes, with ₁ rotated slightly (12°) relative to the NUVEL1A subduction vector, indicating that these earthquakes are occurring in response to regional tectonic forces. On the other hand, stress tensors for earthquake clusters beneath several Katmai cluster volcanoes have vertically oriented ₁ axes, indicating that these events are occurring in response to local, not regional, processes. At Martin-Mageik, vertically oriented ₁ is most consistent with failure under edifice loading conditions in conjunction with localized pore pressure increases associated with hydrothermal circulation cells. At Trident-Novarupta, it is consistent with a number of possible models, including occurrence along fractures formed during the 1912 eruption that now serve as horizontal conduits for migrating fluids and/or volatiles from nearby degassing and cooling magma bodies. At Mount Katmai, it is most consistent with continued seismicity along ring-fracture systems created in the 1912 eruption, perhaps enhanced by circulating hydrothermal fluids and/or seepage from the caldera-filling lake.

This article has been cited by other articles:

				D. C. Roman, S. C. Moran, J. A. Power, and K. V. Cashman Temporal and Spatial Variation of Local Stress Fields before and after the 1992 Eruptions of Crater Peak Vent, Mount Spurr Volcano, Alaska Bulletin of the Seismological Society of America, December 1, 2004; 94(6): 2366 - 2379. [Abstract] [Full Text] [PDF]

				S. C. Moran, J. A. Power, S. D. Stihler, J. J. Sanchez, and J. Caplan-Auerbach Earthquake Triggering at Alaskan Volcanoes Following the 3 November 2002 Denali Fault Earthquake Bulletin of the Seismological Society of America, December 1, 2004; 94(6B): S300 - S309. [Abstract] [Full Text] [PDF]

				Simultaneous Earthquake Swarms and Eruption in Alaska, Fall 1996: Statistical Significance and Inference of a Large Aseismic Slip Event Bulletin of the Seismological Society of America, October 1, 2004; 94(5): 1831 - 1841.