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 (12) Citing Articles via Google Scholar Google Scholar Articles by Hough, S. E. Articles by Johnson, P. Search for Related Content GeoRef GeoRef Citation

The 1998 Earthquake Sequence South of Long Valley Caldera, California: Hints of Magmatic Involvement

U.S. Geological Survey
Pasadena, California

A significant episode of seismic and geodetic unrest took place at Long Valley Caldera, California, beginning in the summer of 1997. Activity through late May of 1998 was concentrated in and around the south moat and the south margin of the resurgent dome. The Sierran Nevada block (SNB) region to the south/southeast remained relatively quiet until a M 5.1 event occurred there on 9 June 1998 (UT). A second M 5.1 event followed on 15 July (UT); both events were followed by appreciable aftershock sequences. An additional, distinct burst of activity began on 1 August 1998. The number of events in the August sequence (over the first week or two) was similar to the aftershock sequence of the 15 July 1998 M 5.1 event, but the later sequence was not associated with any events larger than M 4.3. All of the summer 1998 SNB activity was considered tectonic rather than magmatic; in general the SNB is considered an unlikely location for future eruptions. However, the August sequence—an "aftershock sequence without a mainshock"—is suggestive of a strain event larger than the cumulative seismotectonic strain release. Moreover, a careful examination of waveforms from the August sequence reveals a small handful of events whose spectral signature is strikingly harmonic. We investigate the waveforms of these events using spectral, autocorrelation, and empirical Green's function techniques and conclude that they were most likely associated with a fluid-controlled source. Our observations suggest that there may have been some degree of magma or magma-derived fluid involvement in the 1998 SNB sequence.

This article has been cited by other articles:

				D. C. Templeton and D. S. Dreger Non-Double-Couple Earthquakes in the Long Valley Volcanic Region Bulletin of the Seismological Society of America, February 1, 2006; 96(1): 69 - 79. [Abstract] [Full Text] [PDF]

				D. P. Hill Unrest in Long Valley Caldera, California, 1978-2004 Geological Society, London, Special Publications, January 1, 2006; 269(1): 1 - 24. [Abstract] [PDF]

				Source Properties of Earthquakes near the Salton Sea Triggered by the 16 October 1999 M 7.1 Hector Mine, California, Earthquake Bulletin of the Seismological Society of America, May 1, 2002; 92(4): 1281 - 1289.

				Fault Slip, Seismicity, and Deformation in Mexicali Valley, Baja California, Mexico, after the M 7.1 1999 Hector Mine Earthquake Bulletin of the Seismological Society of America, May 1, 2002; 92(4): 1290 - 1299.

				Observations of Earthquake Source Parameters at 2 km Depth in the Long Valley Caldera, Eastern California Bulletin of the Seismological Society of America, April 1, 2001; 91(2): 165 - 177.