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Thomas L. Holzer

Publications and source records attributed to Thomas L. Holzer.

28 records · Page 2Linked to original sources
USGS1998

The Loma Prieta, California, earthquake of October 17, 1989: Liquefaction

The 1989 Loma Prieta earthquake both reconfirmed the vulnerability of areas in the San Francisco-Monterey Bay region to liquefaction and provided an opportunity to test methodologies for predicting liquefaction that have been developed since the mid-1970's. This vulnerability is documented in the chapter edited by O'Rourke and by the investigators in this chapter who describe case histories of liquefaction damage and warn us about the potential for even greater damage from liquefaction if an earthquake similar to the 1989 Loma Prieta earthquake, but located closer to their study sites, were to occur.

California↗
USGS1996

Seismology, geology, and geotechnical issues

The Hyogoken-Nanbu (Kobe) earthquake of January 17, 1995 (5:46:52 JST) occurred in an area of complex faulting located near Awaji Island and the Hanshin area of Japan (34.607 N, 135.043 E, depth 14.3 km; Japan Meteorological Agency, JMA). The area which is near the urban centers of Kobe City and Osaka is located about 250 km from the Nankai trough, which forms the boundary between the Philippine Sea and Eurasian plates (Figure 2.1.1). The earthquake of magnitude 7.2 (JMA) is the most severe earthquake to affect the region this century. The largest previous earthquake near Kobe City was a magnitude 6.1 which occurred in 1916 on or near the same fault. Other large but distant earthquakes occurred in 1944 and 1946 along the plate boundary (Figure 2.1.1). Numerous faults known to be active in the Quaternary extend throughout the affected region (Figure 2.1.2). However, prior to January 17, 1995 the area was characterized by relatively low seismicity compared with areas near the plate boundaries (Figure 2.1.1). This 1995 earthquake having occurred at considerable distance from the plate margin, can be considered an intraplate event.

Hanshin↗
USGS1994

Piezometer performance at Wildlife liquefaction site, California

In response to an urgent need for field data from instrumented liquefaction sites, the U.S. Geological Survey in 1982 selected and instrumented a site in southern California called the Wildlife site. Two accelerometers (one at ground surface and one at a depth of 7.5 m) and six electrical pore‐pressure transducers (five in a liquefiable silty sand layer) were placed at the site. The November 1987 Superstition Hills earthquake triggered sand boils and the desired instrumental response by generating excess pore‐water pressure that approximately equaled the initial effective overburden pressure. These records are the first from a field site to trace ground motions and pore pressures through the entire liquefaction process. Because pore pressure continued to rise after most of the seismic energy had propagated through the site, questions about the fidelity of the pore‐pressure records have been raised. Because of the importance of the Wildlife records, we reexamine pertinent aspects of the instruments and their placement, review their 1987 response, evaluate and respond to criticisms by Hushmand et al. (1992a, 1992b), and examine analyses of the records by other investigators that are pertinent to an evaluation of the fidelity of the piezometer records. This review concludes that no data or analyses have been developed that convincingly demonstrate that the pore‐pressure piezometers responded incorrectly. Conversely, an analysis by Zeghal and Elgamal (1994) provides strong evidence that the piezometers responded with a high degree of fidelity.

California↗
USGS1994

Predicting earthquake effects—Learning from Northridge and Loma Prieta

The continental United States has been rocked by two particularly damaging earthquakes in the last 4.5 years, Loma Prieta in northern California in 1989 and Northridge in southern California in 1994. Combined losses from these two earthquakes approached $30 billion. Approximately half these losses were reimbursed by the federal government. Because large earthquakes typically overwhelm state resources and place unplanned burdens on the federal government, it is important to learn from these earthquakes how to reduce future losses. My purpose here is to explore a potential implication of the Northridge and Loma Prieta earthquakes for hazard-mitigation strategies: earth scientists should increase their efforts to map hazardous areas within urban regions.

Science↗
USGS1978

Results and interpretation of exploratory drilling near the Picacho Fault, south-central Arizona

Modern surface faulting along the Picacho fault, east of Picacho, Arizona, has been attributed to ground-water withdrawal. In September 1977, three exploratory test holes were drilled 5 km east of Picacho and across the Picacho fault to investigate subsurface conditions and the mechanism of the faulting. The holes were logged by conventional geophysical and geologic methods. Piezometers were set in each hole and have been monitored since September 1977. The drilling indicates that the unconsolidated alluvium beneath the surface fault is approximately 310 m thick. Drilling and piezometer data and an associated seismic refraction survey indicate that the modern faulting is coincident with a preexisting, high-angle, normal fault that offsets units within the alluvium as well as the underlying bedrock. Piezometer and neutron log data indicate that the preexisting fault behaves as a partial ground-water barrier. Monitoring of the piezometers indicates that the magnitude of the man-induced difference in water level across the preexisting fault is seasonal in nature, essentially disappearing during periods of water-level recovery. The magnitude of the seasonal difference in water level, however, appears to be sufficient to account for the modern fault offset by localized differential compaction caused by a difference in water level across the preexisting fault. In addition, repeated level surveys since September 1977 of bench marks across the surface fault and near the piezometers have indicated fault movement that corresponds to fluctuations of water level.

Open-File Report↗
USGS1978

Documentation of potential for surface faulting related to ground-water withdrawal in Las Vegas Valley, Nevada

Leveling data collected in Las Vegas Valley are compatible with the interpretation that ongoing land-surface displacements related to ground-water withdrawal may be precursory to fault offset of the land surface. Zones of potential faulting intersect regions of intense urban development. The degree of risk and the potential economic consequences from possible surface faulting cannot be assessed adequately without additional data and analysis of the relation between surface faulting and ground-water withdrawal.

Nevada↗