Publications

This paper examines the rationale of a method of nonstationary processing and analysis, referred to as the Hilbert-Huang transform (HHT), for its application to a recording-based approach in quantifying influences of soil nonlinearity in site response. In particular, this paper first summarizes symptoms of soil nonlinearity shown in earthquake recordings, reviews the Fourier-based approach to char

This publication makes available a detailed trench log (sheets 1 and 2) of a 110-m trench we excavated in 2004 across a tectonic sag pond in the Hayward fault zone. Also included are revised stratigraphic unit descriptions from this fifth field season of subsurface investigation of the Hayward fault at Tyson's Lagoon (Tule Pond). Preliminary findings based on fieldwork done in 2000 have been publi

We have estimated P-wave and S-wave anelastic attenuation coefficients for the thick, unconsolidated sediments of the Mississippi embayment, central United States, using the spectral distance decay of explosion P and Rayleigh waves. The sediment-trapped P wave, Psed, is observed to ranges of 80 km at 10 Hz, and 1-Hz Rayleigh waves are observed out to 130 km from a 5000-lb borehole explosion in the

We present an updated global earthquake catalogue for stable continental regions (SCRs; i.e. intraplate earthquakes) that is available on the Internet. Our database contains information on location, magnitude, seismic moment and focal mechanisms for over 1300 M (moment magnitude) ≥ 4.5 historic and instrumentally recorded crustal events. Using this updated earthquake database in combination with a

New seismic and geodetic data from Costa Rica provide insight into seismogenic zone processes in Central America, where the Cocos and Caribbean plates converge. Seismic data are from combined land and ocean bottom deployments in the Nicoya peninsula in northern Costa Rica and near the Osa peninsula in southern Costa Rica. In Nicoya, inversion of GPS data suggests two locked patches centered at 14

Although some scientists considered the Ms=7.1 Loma Prieta, Calif., earthquake of 1989 to be an anticipated event, some aspects of the earthquake were surprising. It occurred 17 km beneath the Santa Cruz Mountains along a left-stepping restraining bend in the San Andreas fault system. Rupture on the southwest-dipping fault plane consisted of subequal amounts of right-lateral and reverse motion but

Campbell (1983) demonstrated that site amplification correlates with depths to the 1.0, 1.5, and 2.5 km/s S-wave velocity horizons. To estimate these depths for the Bay Area stations in the PEER/NGA database, we compare the depths to the 3.2 and 4.4 km/s P-wave velocities in the Brocher and others (1997) 3D velocity model with the depths to these horizons determined from 6 refraction lines shot in

The TriNet project, launched in 1997, created an improved, real-time seismic monitoring network in Southern California. Planning of the network began in 1995 (e.g., Heaton et al., 1996), building on the success of the earlier TERRAscope network, which included 24 digital broadband and strong-motion instruments throughout Southern California (e.g., Kanamori et al., 1993). At the end of the five-yea

The Mw 6.5 San Simeon earthquake struck the central California coast on 22 December 2003 at 19:15:56 UTC (11:15:56 am local time.) The epicenter was located 11 km northeast of the town of San Simeon, and 39 km west-northwest of Paso Robles (Figure 1), as reported by the California Integrated Seismic Network (CISN, the California region of the Advanced National Seismic System [ANSS]). The mainshock

The Tacoma fault bounds gravity and aeromagnetic anomalies for 50 km across central Puget lowland from Tacoma to western Kitsap County. Tomography implies at least 6 km of post-Eocene uplift to the north of the fault relative to basinal sedimentary rocks to the south. Coastlines north of the Tacoma fault rose about 1100 years ago during a large earthquake. Abrupt uplift up to several meters caus

The northwest-striking southern Whidbey Island fault zone (SWIF) was mapped previously using borehole data and potential-field anomalies on Whidbey Island and marine seismic surveys beneath surrounding waterways. Abrupt subsidence at a coastal marsh on south-central Whidbey Island suggests that the SWIF experienced a MW 6.5 to 7.0 earthquake about 3000 years ago. Southeast of Whidbey Island, a hyp

We interpret seismic lines and a wide variety of other geological and geophysical data to suggest that the Seattle uplift is a passive-roof duplex. A passive-roof duplex is bounded top and bottom by thrust faults with opposite senses of vergence that form a triangle zone at the leading edge of the advancing thrust sheet. In passive-roof duplexes the roof thrust slips only when the floor thrust rup