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T. Leslie Youd

Publications and source records attributed to T. Leslie Youd.

6 recordsLinked to original sources
USGS2003

The plan to coordinate NEHRP post-earthquake investigations

This is the plan to coordinate domestic and foreign post-earthquake investigations supported by the National Earthquake Hazards Reduction Program (NEHRP). The plan addresses coordination of both the NEHRP agencies—Federal Emergency Management Agency (FEMA), National Institute of Standards and Technology (NIST), National Science Foundation (NSF), and U. S. Geological Survey (USGS)—and their partners. The plan is a framework for both coordinating what is going to be done and identifying responsibilities for post-earthquake investigations. It does not specify what will be done. Coordination is addressed in various time frames ranging from hours to years after an earthquake. The plan includes measures for (1) gaining rapid and general agreement on high-priority research opportunities, and (2) conducting the data gathering and fi eld studies in a coordinated manner. It deals with identifi cation, collection, processing, documentation, archiving, and dissemination of the results of post-earthquake work in a timely manner and easily accessible format.

Circular↗
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↗
USGS1978

Historic ground failures in Northern California triggered by earthquakes

A major source of earthquake-related damage and casualties in northern California has been ground failures generated by the seismic shaking, including landslides, lateral spreads, ground settlement, and surface cracks. The historical record shows that, except for offshore shocks, the geographic area affected and the quantity and general severity of ground failures increase markedly with Richter magnitude. Hence, the largest historical event, the 1906 San Francisco earthquake, has been the most important generator of ground failures. Because of recent population growth and land development in northern California, the potential for damage in future events is enormous compared with that existing in 1906. Reports of the 1906 San Francisco earthquake and other northern California earthquakes and descriptions of ground failures therein are used to (1) identify and clarify the types of ground failures associated with earthquakes, (2) provide a guide for engineers, planners, and others responsible for minimizing seismic hazards, and (3) form a data base for other geotechnical studies of earthquake-triggered pound failures. Geologic, hydrologic, and topographic setting have an important influence on ground failure development as well as distance from the causative fault. Areas especially vulnerable to ground failure in northern California have been oversteepened slopes, such as mountain cliffs, streambanks, and coastal bluffs, and lowland deposits, principally Holocene fluvial deposits, deltaic deposits, and poorly compacted fills. Liquefaction has been the direct cause of most lowland failures. The historical record suggests that ground failures during future large earthquakes are most likely to occur at the same or geologically similar locations as failures during previous earhquakes.

California↗
USGS1977

Reconnaissance report of geotechnical observations for the 4 March 1977 Romanian earthquake

A catastrophic earthquake struck south central Romania at 21:21 hours (9:21 p.m.) local time, March 4, 1977. The tremor collapsed 33 multistory buildings in Bucharest and damaged many other structures to varying degrees. Important damage was inflicted on many other cities and villages, particularly Craiova and Zimnicea. (For locations, see Fig. 1) Over 1,500 deaths resulted from the shock. The epicenter of the shock was preliminarily located at 45.85° N, 26.73° E with a focal depth of 110 km. A preliminary magnitude of 7.2 was assigned to the event. Aftershocks up to approximately magnitude 4 have spread south westward from the epicenter (approximately as far south as Buzau). The focal depths of aftershocks in the southern part of the zone were shallower than the main shock (as shallow as 50 km). A team of nine United States scientists and engineers was sent by the U. S. State Department to make a reconnaissance investigation of earthquake effects and damage. The team consisted of; Charles Culver (team leader) and George Fattal, National Bureau of Standards; Gerald Bowles and Fred Ruud, Bureau of Reclamation; Ernest Dodson, Army Corps of Engineers; Ted Algermissen Chris Rojahn and Les Youd, U. S. Geological Survey; and Karl Steinbrugge, Insurance Services office and a consultant to U.S.G.S. Upon arrival in Romania, the team was divided into groups which generally specialized in the following areas: Culver and Fattal investigated structural damage to buildings. Algermissen and Steinbrugge investigated the general distribution of damage and types of buildings affected in Bucharest. Dodson, Bowles and Ruud investigated damage to dams and hydroelectric power plants. Rojahn collected strong motion records and initiated discussions with the Romanians on the possible development of additional strong motion seismographs. Youd investigated damage to foundations and occurrences of ground failure (landslides, etc.). The groups worked independently of each other. However, there was communication between groups during joint meetings with various Romanian officials and in the evening hours. The purposes of this report are: 1. To summarize geotechnical effects of the earthquake. 2. To outline and justify a proposed United States Romanian cooperative geotechnical program which was considered as part of a broader cooperative program in engineering and seismology. 3. To provide a log of my travels.

Open-File Report↗
USGS1973

Liquefacton

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Earthquake Information Bulletin (USGS)↗