Faulting process of the San Fernando earthquake of February 9, 1971 inferred from static and dynamic near-field displacements
- 1 February 1973
- journal article
- Published by Seismological Society of America (SSA) in Bulletin of the Seismological Society of America
- Vol. 63 (1), 249-269
- https://doi.org/10.1785/bssa0630010249
Abstract
The faulting process of the San Fernando earthquake of February 9, 1971 has been investigated using the following seismic and geodetic data: vertical and horizontal displacements, strain and tilt changes, dynamic ground motions in the near-field, focal mechanism, spatial distribution of aftershocks and features of surface fault breaks. A synthetic study suggests that the earthquake was caused by thrust faulting with a slip of 233° to 244° over a fault plane with dimensions 19 by 14 km, dip 50° to 52° and strike N64° to 70°W, which ruptures the ground surface over a distance of about 12 km. The fracture initiating at the hypocenter of the main shock seems to have propagated radially over the fault plane with a velocity about 2.5 km/sec. A small dislocation less than 30 cm at initiation probably increased rapidly during propagation and reached 3.5 to 4 m at the ground surface. A pronounced uplift and small subsidence of the ground north and south of the fault traces, and the overall pattern of the observed vertical and horizontal displacements can be explained well by the above model, but the recorded strain and tilt offsets are not always consistent with theoretical predictions. The wave forms and amplitudes for some of the integrated ground displacements from accelerograms at the Pacoima Dam and Pasadena are in fairly close agreement with those of the computed displacements. The seismic moment and stress drop of this earthquake were found to be 1.1 × 1026 dyne·cm and 40 to 65 bars, respectively.Keywords
This publication has 17 references indexed in Scilit:
- Determination of effective tectonic stress associated with earthquake faulting. The Tottori earthquake of 1943Physics of the Earth and Planetary Interiors, 1972
- Static and dynamic study of earthquake source mechanism: San Fernando EarthquakeJournal of Geophysical Research, 1972
- Mechanism of underthrusting in southwest Japan: A model of convergent plate interactionsJournal of Geophysical Research, 1971
- Seismological evidence for a lithospheric normal faulting — the Sanriku earthquake of 1933Physics of the Earth and Planetary Interiors, 1971
- Crustal Deformation due to Dislocation in a Multi-layered MediumJournal of Physics of the Earth, 1971
- Seismic displacements near a faultJournal of Geophysical Research, 1968
- The dislocation fault model with a variable discontinuityTectonophysics, 1968
- Surface deformation associated with dip-slip faultingJournal of Geophysical Research, 1966
- Displacements, strains, and tilts at teleseismic distancesPublished by American Geophysical Union (AGU) ,1965
- SOME GEOPHYSICAL APPLICATIONS OF THE ELASTICITY THEORY OF DISLOCATIONSCanadian Journal of Physics, 1958