Report on seismologic field investigations of the 29 June 1992 Little Skull Mountain Earthquake

Meremonte, Mark; Cranswick, Edward; Gomberg, Joan; Worley, David M.; Brooks, Jennifer; Banfill, Robert; Overturf, Dee; Bice, T.

doi:10.3133/ofr93555

Cited by 5 publications

(2 citation statements)

References 3 publications

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“…From August 1978 through September 1995 earthquake monitoring was conducted by the USGS, and later (post 10/1/1992) by NSL, with a regional, analog-telemetry seismic network consisting primarily of vertical component low-dynamic range seismographs. The analog network was in place during the Underground Nuclear Explosion (UNE) testing era at NTS (last announced UNE, September 1992) and during the 1992 M 5.6 Little Skull Mountain earthquake (Meremonte et al, 1995;Smith et al, 2001). The analog network did not include strong motion instrumentation;…”

Section: Finalizing the Earthquake Catalogmentioning

confidence: 99%

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Seismicity in the Vicinity of Yucca Mountain, Nevada, for the Period October 1, 2004 to September 30, 2006

Smith¹

2007

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Section: Finalizing the Earthquake Catalogmentioning

confidence: 99%

“…is the continuing aftershocks of the 1992 M 5.6 Little Skull Mountain earthquake (Meremonte et al, 1995;Smith et al, 2001). The Little Skull Mountain area still contributes the dominant portion of the catalog in terms of numbers of located events.…”

Section: Fy05-06 Earthquakesmentioning

confidence: 99%

Seismicity in the Vicinity of Yucca Mountain, Nevada, for the Period October 1, 2004 to September 30, 2006

Smith¹

2007

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The 1994 Northridge, California, earthquake: Investigation of rupture velocity, risetime, and high‐frequency radiation

Hartzell¹,

Liu²,

Mendoza³

1996

J. Geophys. Res.

143

109

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A hybrid global search algorithm is used to solve the nonlinear problem of calculating slip amplitude, rake, risetime, and rupture time on a finite fault. Thirty‐five strong motion velocity records are inverted by this method over the frequency band from 0.1 to 1.0 Hz for the Northridge earthquake. Four regions of larger‐amplitude slip are identified: one near the hypocenter at a depth of 17 km, a second west of the hypocenter at about the same depth, a third updip from the hypocenter at a depth of 10 km, and a fourth updip from the hypocenter and to the northwest. The results further show an initial fast rupture with a velocity of 2.8 to 3.0 km/s followed by a slow termination of the rupture with velocities of 2.0 to 2.5 km/s. The initial energetic rupture phase lasts for 3 s, extending out 10 km from the hypocenter. Slip near the hypocenter has a short risetime of 0.5 s, which increases to 1.5 s for the major slip areas removed from the hypocentral region. The energetic rupture phase is also shown to be the primary source of high‐frequency radiation (1–15 Hz) by an inversion of acceleration envelopes. The same global search algorithm is used in the envelope inversion to calculate high‐frequency radiation intensity on the fault and rupture time. The rupture timing from the low‐ and high‐frequency inversions is similar, indicating that the high frequencies are produced primarily at the mainshock rupture front. Two major sources of high‐frequency radiation are identified within the energetic rupture phase, one at the hypocenter and another deep source to the west of the hypocenter. The source at the hypocenter is associated with the initiation of rupture and the breaking of a high‐stress‐drop asperity and the second is associated with stopping of the rupture in a westerly direction.

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Urban seismology—Northridge aftershocks recorded by multi-scale arrays of portable digital seismographs

Meremonte

Frankel

Cranswick

et al. 1996

Bulletin of the Seismological Society of America

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We deployed portable digital seismographs in the San Fernando Valley (SFV), the Los Angeles basin (LAB), and surrounding hills to record aftershocks of the 17 January 1994 Northridge California earthquake. The purpose of the deployment was to investigate factors relevant to seismic zonation in urban areas, such as site amplification, sedimentary basin effects, and the variability of ground motion over short baselines. We placed seismographs at 47 sites (not all concurrently) and recorded about 290 earthquakes with magnitudes up to 5.1 at five stations or more. We deployed widely spaced stations for profiles across the San Fernando Valley, as well as five dense arrays (apertures of 200 to 500 m) in areas of high damage, such as the collapsed Interstate 10 overpass, Sherman Oaks, and the collapsed parking garage at CalState Northridge. Aftershock data analysis indicates a correlation of site amplification with mainshock damage. We found several cases where the site amplification depended on the azimuth of the aftershock, possibly indicating focusing from basin structures. For the parking garage array, we found large ground-motion variabilities (a factor of 2) over 200-m distances for sites on the same mapped soil unit. Array analysis of the aftershock seismograms demonstrates that sizable arrivals after the direct S waves consist of surface waves traveling from the same azimuth as that of the epicenter. These surface waves increase the duration of motions and can have frequencies as high as about 4 Hz. For the events studied here, we do not observe large arrivals reflected from the southern edge of the San Fernando Valley.

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Report on seismologic field investigations of the 29 June 1992 Little Skull Mountain Earthquake

Abstract: This report is preliminary and has not been reviewed for conformity with U.S. Geological Survey editorial standards and stratigraphic nomenclature. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the USGS.

Cited by 5 publications

References 3 publications

Seismicity in the Vicinity of Yucca Mountain, Nevada, for the Period October 1, 2004 to September 30, 2006

Seismicity in the Vicinity of Yucca Mountain, Nevada, for the Period October 1, 2004 to September 30, 2006

The 1994 Northridge, California, earthquake: Investigation of rupture velocity, risetime, and high‐frequency radiation

Urban seismology—Northridge aftershocks recorded by multi-scale arrays of portable digital seismographs

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