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2004 Adobe Hills Swarm

Details | Ground motions | Maps | Waveforms | Related links

Information from the CISN
Date & Time (Local): 2004/09/18
04:02:17 PM (PDT)
Date & Time (UTC): 2004/09/18
23:02:17 (UTC)
Location: 23 miles SE of Bodie, CA
38.009N, 118.679W
Depth (km): 7.6
Magnitude: 5.5 Mw


Map of seismicity near Adode Hill October 8: Today a M4.7 earthquake occurred in the area of the Adobe Hills at 08:45 PM. It was followed by numerous aftershocks, include events of M3.5, 3.0, 3.3, and 3.0. In contrast to the events of September, these earthquakes appear to be a north to northwest trending plane.

September 23: The Nevada Bureau of Mines and Geology reported today the discovery of minor cracks related to fault movement during the swarm. According to NBMG, "Three groups of cracks were found over an 800 m distance. Two groups were on a fault with very subtle surface expression, and the easternmost group occurred along a very prominent strike-slip fault. The cracks are minor, commonly opened only 2 to 5 mm wide, but are significant because they align along faults, are unique in the area canvassed, and show tectonic patterns. Several of the cracks have right-stepping patterns and a couple of cracks had shifted left-laterally by as much as 3 mm"

September 20: An M4.8 occurred this morning at 9:51 AM local time. Over 600 events have occurred in this swarm as of noon today. Scientific background on this swarm and maps of background seismicity are now available.

September 18: An earthquake sequence is occurring near the California/Nevada border, just east of Mono Lake and beneath the Adobe Hills. This series of events started on 9/18 at 12:02 local time with an M2.3 earthquake. It was followed by an M4.1 (12:08 AM), the 5.5 at (04:02 PM - this event), a 5.4 (04:43 PM), and a 4.1 (04:47 PM) as well as numerous events less than M4.

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Ground Motions

The CISN Northern California Management Center produces ShakeMaps for events of M3.5 and higher. ShakeMaps are based on the observed ground motions from seismic instruments combined with predicted motions in areas without sensors. In this swarm ShakeMaps have been produced for several events - only the largest events are listed here.

The CISN Engineering Data Center produces reports showing details of ground motions for events of interest. Thus far, they have generated two Internet Quick Reports (IQR) for events in the swarm:

Many earthquakes in this swarm have been widely felt. People with Internet access can report their observations of shaking and damage through the Did You Feel It? Web site. In the links below, you can see the maps illustrating the reported intensities for several events in this sequence. Unlike the ShakeMaps - which are based on data from seismic instruments - these maps are based on human observations. You can contribute to these data by filling out the form for each event.

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These links will take you to seismocams showing current earthquake activity.

Below are links to waveforms for the M5.5 and 5.4 events.

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Related Links

CISN Northern California Management Center and the Nevada Seismological Laboratory

CISN Earthquake Reports

California Integrated Seismic Network

CGS USGS OES Caltech UC Berkeley