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Roger D. Borcherdt

Publications and source records attributed to Roger D. Borcherdt.

At least 37 records · Page 2Linked to original sources
USGS2005

Preliminary report on the 28 September 2004, M 6.0 Parkfield, California earthquake

The M w 6.0 Parkfield earthquake struck central California at 17:15:14 UTC on 28 September 2004. The epicenter was located 11 km southeast of the rural town of Parkfield, adjacent to Gold Hill and on the San Andreas Fault ( Figure 1 ). The California Integrated Seismic Network (CISN) reported that the hypocenter was located at 35.819°N, 120.364°W at a depth of 8.8 km. From the distribution of aftershocks and from models of seismograms, strain changes, and geodetic displacements from the earthquake, it appears that the rupture propagated to the northwest along the San Andreas Fault from its hypocenter beneath Gold Hill to Middle Mountain. Because of the earthquake's moderate size and the low population density, only minimal damage was reported, but strong ground motions of approximately 1 g were recorded at a few isolated points (Shakal et al. , 2005, this issue).

California↗
USGS2003

Seismic design provisions and guidelines in the United States: A prologue

Seismic design provisions and guidelines are the basis for reduction of potentially devastating losses of life and property from earthquakes. Six tragic earthquakes since 1985, affecting Mexico, Armenia, the United States, Japan, Turkey, and Taiwan, caused combined property losses exceeding $320 billion and loss of lives exceeding 143,900. These losses emphasize the need to improve the earthquake resistance of the built environment in zones of high seismic risk. With present population exceeding 290 million in major earthquake zones and world population expected to increase by 2 to 4 billion people in the next 50 years, losses from future earthquakes can be expected to reach even greater levels if worldwide improvements in earthquake resistance are not made.

International Geophysics↗
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↗
USGS2002

Shear-wave velocity compilation for Northridge strong-motion recording sites

Borehole and other geotechnical information collected at the strong-motion recording sites of the Northridge earthquake of January 17, 1994 provide an important new basis for the characterization of local site conditions. These geotechnical data, when combined with analysis of strong-motion recordings, provide an empirical basis to evaluate site coefficients used in current versions of US building codes. Shear-wave-velocity estimates to a depth of 30 meters are derived for 176 strong-motion recording sites. The estimates are based on borehole shear-velocity logs, physical property logs, correlations with physical properties and digital geologic maps. Surface-wave velocity measurements and standard penetration data are compiled as additional constraints. These data as compiled from a variety of databases are presented via GIS maps and corresponding tables to facilitate use by other investigators.

California↗
USGS2001

Integrated surface and borehole strong-motion, soil-response arrays in San Francisco, California

An integrated set of four borehole arrays and ten surface installations is installed in the city of San Francisco, California to measure the response of soft-soil deposits to strong earthquake ground motions. The borehole arrays extend through thick layers of softwater-saturated soils of Holocene age and older more consolidated soils of Pleistocene age into bedrock at depths up to 100 m. The surface installations are configured in pairs to provide simultaneous comparative surface measurements of soft soils and nearby rock. The rock locations also permit comparative measurements of rock as observed at the surface and in nearby boreholes. Complementary structural response arrays alsoare installed near each array. The arrays are designed to address a wide variety of scientific and engineering issues, and especially the issue of anelastic and nonlinear soil response at high strain levels. Exact anelastic models have been developed to account for contrasts in anelastic properties at boundaries and the resultant inhomogeneity of propagating wave fields. These models predict that significant amounts of energy may be trapped in soil basins with resultant larger amplifications than can be predicted using conventional homogeneous wave-field models with damping. Results of these models are discussed.

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↗
USGS1995

Seismic maps foster landmark legislation

When a powerful earthquake strikes an urban region, damage concentrates not only near the quake's source. Damage can also occur many miles from the source in areas of soft ground. In recent years, scientists have developed ways to identify and map these areas of high seismic hazard. This advance has spurred pioneering legislation to reduce earthquake losses in areas of greatest hazard.

Fact Sheet↗
USGS1995

Near real-time monitoring of seismic events and status of portable digital recorders using satellite telemetry

Near real-time monitoring of seismic events and status of portable 16-bit digital recorders has been established for arrays near Parkfield, Mammoth Lakes, and San Francisco, California. This monitoring system provides near real-time seismic event identification (rough location and magnitude) and a cost-effective means to maintain arrays at near 100% operational level. Principal objectives in the design of this system have been portability and low-cost telemetry. The system has been developed to use portable digital seismic recorders ( GEOS —General Earthquake Observation System) and portable data collection platforms ( DCP 's) for the Geostationary Operational Environmental Satellite (GEOS) telemetry system. Data are transferred asynchronously from the GEOS seismic system through a microprocessor-controlled interface every 10 min. The interface stores, determines priority, converts, and synchronously transfers these data to a Sutron Corp. model 8004 DCP for transmission through the GEOS satellite telemetry system. Event parameters include trigger time, peak amplitude, time of peak amplitude, and event duration. Instrument configuration parameters, transmitted at system start-up time and every 24 hr, include recording parameters, trigger parameters, GEOS software version, clock reference, and location parameter. Instrument status includes battery voltage, number of events, and percentage of tape usage. These data are transmitted as appropriate to the U.S. Geological Survey satellite downlink and computers located in Menlo Park, California, where they are processed and displayed.

Bulletin of the Seismological Society of America↗
USGS1995

The Hanshin-Awaji Earthquake of January 17, 1995: Performance of lifelines

This report describes the damage to lifelines caused by the 1995 Hanshin-Awaji (Kobe) earthquake in Japan. It begins with a summary of the earthquake's seismological characteristics which is followed by separate chapters that focus on the performance of lifelines in the affected region. In order of presentation, individual chapters discuss the damage to: 1) electric power networks; 2) gas delivery systems; 3) hospitals (considered as a system composed of building/architectural components, as well as communication and support systems); 4) telecommunication systems; 5) transportation systems; and 6) water supply systems and wastewater systems. The transportation section includes three subsections: airport facilities, highways and bridges, and underground rapid transit systems. For each lifeline, an overview of the system is given, indicating the owner/operator, the location and extent of the service area, the number of households and industrial/commercial customers served. In addition to descriptions of the individual system, design criteria for the physical components of the individual systems are provided, including a comparison of the differences between the US and Japanese systems. The performance of each lifeline system is discussed with reference to seismic damage, emergency response, service interruption and restoration.

Hanshin↗
USGS1995

Seismological and engineering aspects of the 1995 Hyogoken-Nanbu (Kobe) earthquake

Immediately following the Jan. 17, 1995, Kobe earthquake, a reconnaissance team was organized under the auspices of the Earthquake Hazard Mitigation Program of the Engineering Directorate of the National Science Foundation. The mission of the team was to provide a timely, first-hand overview of the type and extent of the damage, and to provide the necessary background information for future research and for U.S.-Japan cooperation in earthquake engineering. Additional information was gathered through participation in U.S.-Japan seminars and workshops, and through collaboration with researchers and practicing engineers in Japan. The research team has focused its efforts on seismology, strong ground motion, geotechnical engineering, and structural engineering. This report provides summaries of the findings in these subject areas.

Hanshin↗
USGS1994

Estimates of site-dependent response spectra for design (methodology and justification)

Recent borehole-geotechnical data and strong-motion measurements constitute a new empirical basis to account for local geological conditions in earthquake-resistant design and site-dependent, building-code provisions. They provide new unambiguous definitions of site classes and rigorous empirical estimates of site-dependent amplification factors in terms of mean shear-wave velocity. A simple four-step methodology for estimating site-dependent response spectra is specified herein. Alternative techniques and commentary are presented for each step to facilitate application of the methodology for different purposes. Justification for the methodology is provided in terms of definitions for the new site classes and derivations of simple empirical equations for amplification as a function of mean shear-wave velocity and input ground-motion level. These new results provide a rigorous framework for improving estimates of site-dependent response spectra for design, site-dependent building-code provisions, and predictive maps of strong ground shaking for purposes of earthquake hazard mitigation.

California↗
USGS1994

Measurements of P and S wave fronts from the dense three-dimensional array at Garni, Armenia

The P - and S -wave arrivals from local earthquakes were studied using an array of 10 three-component instruments in and around a tunnel at Garni Observatory, Armenia. The array has a three-dimensional configuration with lateral dimensions of 300 to 500 m and a depth extent of 100 m. Estimates of the horizontal and vertical components of slowness for P and S wave fronts were used to determine the angles of approach and the propagation velocity. The results showed that the region around the array has low average velocities for both the P (1.43 km/sec) and S (0.61 km/sec) waves, so wave fronts approach the array at steep angles of incidence. Waveforms from one event show clear reflections from the free surface for both P and S waves. The timing of these reflections gives the velocity variation with depth within the array. We estimated a P velocity of 0.33 km/sec within a few meters of the surface, increasing to several kilometers per second for the deepest portion of the array. Local site variations can greatly complicate the high-frequency waveforms, even for tunnel stations in bedrock. The S waves exhibit stronger site dependent waveforms and time delays than do the P waves.

Garni↗
USGS1994

Seismic velocities and geologic logs from boreholes at three downhole arrays in San Francisco, California

The Loma Prieta earthquake of October 17, 1989 (1704 PST), has reinforced observations made by Wood and others (1908) after the 1906 San Francisco earthquake, that poor ground conditions (soft soil) increase the likelihood of shaking damage to structures. Since 1908 many studies (for example Borcherdt, 1970, Borcherdt and Gibbs, 1976, Borcherdt and Glassmoyer, 1992) have shown that soft soils amplify seismic waves at frequencies that can be damaging to structures. Damage in the City of San Francisco from the Loma Prieta earthquake was concentrated in the Marina District, the Embarcadero, and the China Basin areas. Each of these areas, to some degree, is underlain by soft soil deposits. These concentrations of damage raise important questions regarding the amplification effects of such deposits at damaging levels of motion. Unfortunately, no strong-motion recordings were obtained in these areas during the Loma Prieta earthquake and only a limited number (< 10) have been obtained on other soft soil sites in the United States. Consequently, important questions exist regarding the response of such deposits during damaging earthquakes, especially questions regarding the nonlinear soil response. Towards developing a data set to address these important questions, borehole strong-motion arrays have been installed at three locations. These arrays consist of groups of wide-dynamic-range pore-pressure transducers and three-component accelerometers, the outputs of which are recorded digitally. The arrays are designed to provide an integrated set of data on ground shaking, liquifaction-induced ground failure, and structural response. This report describes the detailed geologic, seismic, and material-property determinations derived at each of these sites.

California↗