[1] The M w 6.8 Tottori earthquake, Japan, does not exhibit any surface trace but was particularly well instrumented. Strong motion displacement records and GPS coseismic data are used to constrain the evolution of the slip on the fault plane in time and space. We adopt in this study a two-plane fault geometry based on aftershock distributions and analysis of close station records. In a first step, our inversion allowed surface slip. The model obtained has a significant surface slip, which contradicts the absence of clear surface slip reported by geologists. In a second step, models with no slip at the surface (buried faults), compatible with geological observations, have been tested. The tests with different fault depths show that when slip is allowed to occur close to the surface, the fit to seismological and geodetic data is increased. These tests confirm that slip actually occurred at shallow depth. Despite the nonuniqueness of the solution, all the inverted source models show (1) a large slip amplitude patch at a depth of about 4-5 km and (2) relatively small slip in the hypocentral area. The rupture velocity is about 2750 m/s in the asperity region. The total rupture duration is about 8 s. The slip distribution seems to be controlled by the variation of fault properties with depth. Another feature that could control the rupture of this earthquake is a fault plane almost perpendicular to the main fault NW of the epicenter, which apparently inhibits further rupture propagation.

The Boumerdes earthquake occurred on a fault whose precise location, offshore the Algerian coast, was unknown. Geodetic data are used to determine the absolute position of the fault. The fault might emerge at about 15 km offshore. Accelerograms are used to infer the space‐time history of the rupture using a two‐step inversion in the spectral domain. The observed strong motion records agree with the synthetics for the fault location inferred from geodetic data. The fault plane ruptured for about 18 seconds. The slip distribution on the fault indicates one asperity northwest of the hypocenter with maximum slip amplitude about 3 m. This asperity is probably responsible for most of the damage. Another asperity with slightly smaller slip amplitude is located southeast of the hypocenter. The rupture stops its westward propagation close to the Thenia fault, a structure almost perpendicular to the main fault.

No abstract

No abstract

No abstract