Resultados del procesamiento de los acelerogramas del Instituto Nacional de Seguros. Sismo de Golfito, 3 de abril de 1983

La información digital está disponible para uso en investigación y desarrollo de medidas de mitigación del efecto de los terremotos en zonas urbanas.Procesamiento de los registros de aceleración obtenidos en la estación acelerográfica instalada por la Universidad de Costa Rica en un edificio de concreto reforzado (sede central del Instituto Nacional de Seguros). La estación consiste de dos acelerógrafos interconectados, el primero instalado en el sótano del edificio y el segundo en el nivel 14 del edificio. Se presentan los resultados en la forma de gráficos de desplazamiento, velocidad y aceleración obtenidos de ambos instrumentos. También se presentan los espectros de respuesta y de Fourier a partir de la información registrada.California Strong Motion Instrumentation Program///Estados UnidosUniversidad de Costa Rica//UCR/Costa RicaUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ingeniería::Instituto Investigaciones en Ingeniería (INII

Processed Strong-Motion Records from the Limón, Costa Rica Earthquake of 22 April 1991

Están disponibles los registros digitales obtenidos para uso de los investigadores interesados en estudiar la severidad del terremoto desde el punto de vista instrumental. Se incluyen los acelerogramas obtenidos con equipo Kinemetrics SMA-1 y sus correspondientes integraciones, velocidades y desplazamientos. Se trata de archivos de caracteres ASCII fácilmente legible por medio de diferentes rutinas de análisis de datos.Strong-motion records were recovered from 15 accelerographs at 14 stations operated by the Strong Motion Instrumentation Program of the Earthquake Engineering Laboratory (EEL) at the University of Costa Rica (Santana and others, 1991) following the damaging Limón, Costa Rica earthquake of April 22, 1991. The sites range in epicentral distance from 73 to 160 km; peak horizontal accelerations at ground level ranged from 0.03 to 0.27 g. The accelerograms are characterized by long duration of strong shaking, of approximately 30 seconds. An extensive strong motion data set from a moment magnitude (Mw) 7.5 earthquake is rare. Because of the importance of these data not only to Costa Rica but also to California, the California Strong Motion Instrumentation Program (CSMIP), in cooperation with the University of Costa Rica, digitized and processed these data for distribution to engineers, seismologists and others concerned with the seismic safety problem. This processed data is the second extensive set of data from an earthquake with magnitude between the magnitude 7 Lorna Prieta earthquake and the magnitude 7.8 Chile and Tabas, Iran earthquakes.Universidad de Costa Rica/[]/UCR/Costa RicaUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ingeniería::Instituto Investigaciones en Ingeniería (INII

A Study of Possible Ground-Motion Amplification at the Coyote Lake Dam, California

Abstract The abutment site at the Coyote Lake Dam recorded an unusually large peak acceleration of 1.29g during the 1984 Morgan Hill earthquake. Following this earthquake another strong-motion station was installed about 700 m downstream from the abutment station. We study all events (seven) recorded on these stations, using ratios of peak accelerations, spectral ratios, and particle motion polarization (using holograms) to investigate the relative ground motion at the two sites. We find that in all but one case the motion at the abutment site is larger than the downstream site over a broad frequency band. The polarizations are similar for the two sites for a given event, but can vary from one event to another. This suggests that the dam itself is not strongly influencing the records. Although we can be sure that the relative motion is usually larger at the abutment site, we cannot conclude that there is anomalous site amplification at the abutment site. The downstream site could have lowerthan-usual near-surface amplifications. On the other hand, the geology near the abutment site is extremely complex and includes fault slivers, with rapid lateral changes in materials and presumably seismic velocities. For this reason alone, the abutment site should not be considered a normal free-field site

The 1987 Whittier Narrows Earthquake in the Los Angeles Metropolitan Area, California

The Whittier Narrows earthquake sequence (local magnitude, M_L = 5.9), which caused over $358-million damage, indicates that assessments of earthquake hazards in the Los Angeles metropolitan area may be underestimated. The sequence ruptured a previously unidentified thrust fault that may be part of a large system of thrust faults that extends across the entire east-west length of the northern margin of the Los Angeles basin. Peak horizontal accelerations from the main shock, which were measured at ground level and in structures, were as high as 0.6g (where g is the acceleration of gravity at sea level) within 50 kilometers of the epicenter. The distribution of the modified Mercalli intensity VII reflects a broad north-south elongated zone of damage that is approximately centered on the main shock epicenter