Contribution of strong movements and geodesy to the study of seismic failure physics: application to the analysis of seismic hazard.
Bruno HERNANDEZ, doctorate thesis of the University of Joseph Fourier - Grenoble I (Speciality: Geophysics - Geochemistry - Geomechanics) defended on the 6th October 2000.
This work presents seismic source studies using near?field data. In accordance with the quality and the quantitv of available data we developped and applied various methods to characterize the seismic source. Macroseismic data are used to verify if simple and robust methods used on recent instrumental earthquakes may provide a good tool to calibrate historical events in France. These data are often used to characterize earthquakes to be taken into account for seismic hazard assessment in moderate seismicity regions. Geodetic data (SAR, GPS) are used to estimate the slip distribution on the fault during the 1992, Landers, California earthquake. These data are also used to precise the location and the geometry of the main events of the 1997, Colfiorito, central Italy, earthquake sequence. Finally, the strong motions contain the most complete information about rupture process. These data are used to discriminate between two possible fault planes of the 1999, north India, Chamoli earthquake. The strong motions recorded close to the 1999, Mexico, Oaxaca earthquake are used to constrain the rupture history. Strong motions are also used in combination with geodetic data to access the rupture history of the Landers earthquake and the main events of the Colfiorito seismic sequence. For the Landers earthquake, the data quality and complementarity offered the possibility to describe the rupture development with accuracy. The large heterogeneities in both slip amplitude and rupture velocity variations suggest that the
rupture propagates by breaking successive asperities rather than by propagating like a pulse at constant velocity. The rupture front slows as it encounters barriers and accelerates within main asperities.