A. Gardi, ENS (IPGP) R. Madariaga ENS Ch. Vigny ENS A. RudloffENS A. Lemoine DGF (BRGM) J. Campos DGF PICS CNRS-CONICYT ACI Catnat CNRS ANR Chile Sismicidad.

Presentación del tema: "A. Gardi, ENS (IPGP) R. Madariaga ENS Ch. Vigny ENS A. RudloffENS A. Lemoine DGF (BRGM) J. Campos DGF PICS CNRS-CONICYT ACI Catnat CNRS ANR Chile Sismicidad."— Transcripción de la presentación:

1 A. Gardi, ENS (IPGP) R. Madariaga ENS Ch. Vigny ENS A. RudloffENS A. Lemoine DGF (BRGM) J. Campos DGF PICS CNRS-CONICYT ACI Catnat CNRS ANR Chile Sismicidad y deformación recientes del Centro- Norte de Chile: ¿Estamos asistiendo a la preparación de un terremoto?

2 Grandes sismos de Chile 1868-2005 Nuestra zona de estudio 2005

3 Seismicity of central Chile 1995-2004 Source: DGF

4 17301730 1943 1730 1971-85 1928 1906 1997 La sismicidad no seleccionada de Chile Central 1973-2004

5 There are three catalogs to study NEIC this catalog is complete only for M>5.5 from 1970 and from M>4 in the last few years Centennial catalog complete for M>7 since 1900 and for M>6 since ISC not yet fully analysed

6 Sismicidad entre 1900 y 2006 b=0.8

7 Sismicidad del Catálogo Centennial M>8 M>7 M>6 Recent events

8 Mecanismos de foco desde 1997 Harvard CMT

9 Punitaqui 97

10 WWSSN 1985 1997

11 Diferentes tipos de sismicidad de Chile Central

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13 Punitaqui, 15/10/97 Sismos principales de la secuencia de Coquimbo (1997-2006) July 97 10 sismos de subduccion con M>6. 1 sismo de compresion

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16 Desacuerdo fundamental entre la velocidad de la placa y el movimiento en Ovalle

17 La velocidad de subducción desde 1993 es 2 veces menor que la convergencia, porqué?

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20 Possible models of intermediate depth seismicity Tension before thrust event Compression after thrust Fracture model

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22 Coulomb stress applied by continuous slip at depth on the Fault of the Punitaqui earthquake Chilean seismicity is driven by continuous slip of the Nazca plate with respect to the South American Continent. The stresses due to continuous slip at depth load the Nazca plate producing earthquakes like that of Punitaqui of 15 October 1997 and all the others in fact..

23 July 97 15/10/97 23/06/03

24 1997

25 Relocated seismicity 1992-2004 15 Oct 97

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27 Punitaqui earthquake (15/10/1997) 07/97 1997-2003 Seismicity from local network Jan 1999 From Pardo et al, 2003

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30 Un sismo ‘extra ñ o’, 10 de Enero de 2004 Sismo de falla normal A 50 km de profundidad ¿Previsible? 10 Ene 04 8 Dic 04

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32 Conclusions 5 or 6 interplate thrust events of M~ 6.5 in July 97 were followed by a large slab push event in october 1997. Did they trigger it? The slab push event is clearly favored by aseismic slip at depth The slab push event triggered abundant plate interface events that are still in progress Intermediate depth events are more likely due to aseismic slip rather than long range stress transfer during the seismic cycle Continuous aseismic slip is an essential element of stress transfer in subduction zones. Coulomb stress changes explain well the current seismicity in the Coquimbo region in central Chile

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