The 13 January 2001 El Salvador earthquake: A multidata analysis

• Published in: Journal of Geophysical Research 2003-04, Vol.108 (B4), p.ESE7.1-n/a
• Main Authors: Vallée, Martin, Bouchon, Michel, Schwartz, Susan Y.
• Format: Article
• Language: English
• Subjects: Earth Sciences; Earth, ocean, space; Earthquakes, seismology; El Salvador; empirical Green function; Engineering and environment geology. Geothermics; Exact sciences and technology; Internal geophysics; inversion; Natural hazards: prediction, damages, etc; neighborhood algorithm; Sciences of the Universe; source kinematics; subduction zone
• ISSN: 0148-0227; 2169-9313; 2156-2202; 2169-9356
• DOI: 10.1029/2002JB001922

On 13 January 2001, a large normal faulting intermediate depth event (Mw = 7.7) occurred 40 km off the El Salvadorian coast (Central America). We analyze this earthquake using teleseismic, regional, and local data. We first build a kinematic source model by simultaneously inverting P and SH displacement waveforms and source time functions derived from surface waves using an empirical Green's function analysis. In an attempt to discriminate between the two nodal planes (30° trenchward dipping and 60° landward dipping), we perform identical inversions using both possible fault planes. After relocating the hypocentral depth at 54 km, we retrieve the kinematic features of the rupture using a combination of the Neighborhood algorithm of Sambridge [1999] and the Simplex method allowing for variable rupture velocity and slip. We find updip rupture propagation yielding a centroid depth around 47 km for both assumed fault planes with a larger variance reduction obtained using the 60° landward dipping nodal plane. We test the two possible fault models using regional broadband data and near‐field accelerograms provided by Universidad Centro Americana [2001]. Near‐field data confirm that the steeper landward dipping nodal plane is preferred. Rupture propagated mostly updip and to the northwest, resulting in a main moment release zone of approximately 25 km × 50 km with an average slip of ∼3.5 m. The large slip occurs near the interplate interface at a location where the slab steepens dip significantly. The occurrence of this event is well‐explained by bending of the subducting plate.