First results from teleseismic and geodetic data.

one of the largesl el-ents during this century in lhe region, \\here the historical record contains a sequence of two great subduction earthquakes 01 = 8 5- 9) in 1868 (Soulhern Peni) and 1877 (Yonhern Chile). The 1995 earthquake ruptured h e soulhemmost portion of a seismic gap in Yonhern Chile, between lSCS and 2jCS, a region that we had a l read ~ selected as a target for a study of the seismic cycle and a search for seismic precursors. The project included a GPS net~iork \i.ith about 50 bench marks col7ering a region nearly 900 km long w-S) and 200 km wide (E-\V). Founeen of these marks were re-sun.e!.ed ~ ~ i t h GPS afier the 1995 eanhquake during a ten day period (August 12 to 23) to characterize the deformadon. Comparison with 1992 positions indicate relati1.e horizontal displacement of the coastal bench mark to\iards the trench of the order of 0.7 m. Bench marks located inland subsided se~.eral tens of cm. The bench mark located in hfejillones Peninsula was uplifted by more than l 5 cm. Teleseismic My 1iaI.e modelling of \'BB records gi1.e~ a focal mechanism uith F8"E strike, 19 ' dip, and 1 10 ° rake. The source time function s h o ~. s three distinct episodes of moment release. There is southward directi\ity with a\.erage rupture \,elocily of 3.3 km S-l. Modelling the displacement field using a dislwction with uniform slip in elanic half-space suggeas a rupture zone estending to a depth no greater than 50 km with X-S lengh of-18