Fault Mechanics and Seismic Hazard in the Rift of Corinth, Greece

Pascal Bernard Institut de Physique du Globe de Paris, France

and the Corinth Rift Laboratory (CRL) group Seismicity 1965-2000 - M>5

CORINTH RIFT

1.5 cm/yr 1.0 cm/yr

Briole et al., 2003 CORINTH RIFT LABORATORY (CRL) PROJECT

GDR-CORINTHE: CNRS – IFP - IRSN ICDP E.C. projects since 1997: 30 institutions CORSEIS, DG-LAB, 3F, AEGIS, ASSEM, 3HAZ SHORT TERM FAULT MECHANICS: - Seismic and aseismic slip on faults - Fluid/ Fault interactions - Transients - Crustal structure - fault mechanics - seismicity

SEISMIC HAZARD -Seismic gap and intermediate term prediction -Strong motion amplification and non-linear response in soft soils W E

Aigion fault

Helike fault Mamoussia fault Helike Fault scarp

Aigion City

E W Aigion Fault scarp Dip: 60°

Helike Fault scarp

N AIGION FAULT AIG10 BOREHOLE SCARP 1000 m

Dip: 60° soft sediments N

conglomerate

limestone

Z=1000 m SOUTH NORTH

Seismicity July-August 1991 Rigo, 1996; Lemeur, 1999

- listric normal faults ? - detachment ? M=5.3 Target area M=6.2 Aigion M=5.8 DIP ANGLE: 30-35°

z SOFT SOIL AMPLIFICATION Soft Soil Accelerometric Array CORSSA

Pitilakis et al., 2004 M=3.5, D=13 km Z=0 m

14 m

31 m

57 m

178 m

5 surface 14m Spectral 31m 57m Amplification 2 reference: Z=178 m

Pitilakis et al., 2003 0.5 g

0,50 Computed 0,45 Tp = 0.1s 0,40 Tp = 0.3s PGA surface Tp = 0.5s 0,35 diagw nios 14L-0.1g

) 14L-0.2g

g 0,30 14L-0.3g

ce ( 14L-0.4g a f

r 0,25 14L-0.5g u

s 14T-0.1g A

G 14T-0.2g 0,20 P 14T-0.3g 14T-0.4g 0,15 14T-0.5g Arg83 0,10 Sep99 De c 1 4L De c 1 4T 0,05 Ric k15

0,00 0,00 0,05 0,10 0,15 0,20 0,25 0,30 0,35 0,40 0,45 0,50 PGA bedrockPGA bedrock (g )– 180 m 0.5 g

Normalized acceleration response spectra at the surface (input Dec14T) 4

Design spectra of the Hellenic code PGA=0.1g 3 PGA=0.2g A PGA=0.3g PG / 2 Bedrock Input:

A PGA=0.4g

PS PGA=0.5g 1 ΕΑΚ2000-Γ Aigion 1995 record, 0 0 0,5 1 1,5 2 2,5 3 M=6.2 Period (s )

Pitilakis et al., 2003 MONITORING THE ACTIVITY OF THE RIFT SEISMOLOGICAL AND ACCELEROMETRIC ARRAYS

Lyon-Caen et al. 2004 CORSEIS project SEISMICITY 2001-2002

10 km

Lyon-Caen et al., 2004 SEISMICITY 2001-2002

WEST

CENTER

LOCKED

EAST SLIPPING Bernard et al., 2004 W

Locked and aseismic

Low seismicity rate

High seismicity rate « Brittle » creep Silent creep Bernard et al., 2004 Briole et al., 2001 Modelling of the GPS data – 1990-2000

SOUTH NORTH 1.0 -1.5 cm/yr LOCKED

mm/yr 1.0-1.5 cm/yr 1.5 cm/yr

Briole et al., 2001 S N

Latorre, 2004

Phyllade nappe ? 1817

1861 1888

120 years : slip 1.80 m

recent strain acceleration >250 years : slip > 4.5 m aseismic strain release TRANSIENT PROCESSES SPRING 2001 SEISMIC SWARM

Lyon-Caen et al., 2003 17-23 January 2004 - seismic swarm

Aigion Helike

Helike Aigion

Bouin et al., 2004 Continuous GPS

2003 2004

Briole et 2 cm al., 2004 HIGH RESOLUTION BOREHOLE STRAINMETER AND LONG BASE TILMETER

Trizonia island

Bernard et al., 2004 RECORDS OF EARTH AND SEA TIDE

24 h

STRAIN

TILT

Boudin et al., 2004 STRAIN ANOMALY – 3/12/2002 24 h

30 s Earthquake M=3.5

4x10-7

2 h

2 h Bernard et al., 2004 SEISMIC SWARM Max: M=3.5

Aseismic strain: Equivalent source moment magnitude: M = 5 +- 0.5

2002 Bernard et al., 2004 PORE PRESSURE MEASUREMENT IN AIG10

- clay/radiolarite smearing in the fault zone - 5 MPa overpressure - slow water flow (no Tritium) - no mantellic signature (He)

dip 60°

Cornet et al., 2004 Moretti et al., 2004 0.01 Bar 24 h RECORD OF THE EARTH AND SEA TIDE

10 min RECORD OF THE 2003 ALEUTIAN EARTHQUAKE M=7.5

Cornet et al., 2004 Dynamic pressure

Hydrophone

Cornet et al., 2004 INSTRUMENTATION WITHIN AND BELOW

THE FAULT ZONE - planned: 2005

Cornet et al., 2004 Deep Geophysical Borehole Project

- thisstheomelayer-P seismichylladeactive sli pfaults sswarmsNappe at a arevelocity may and dip bepmoderateingclose a candidate 60° to and thearthquakese rootinload for ingtheg i velocitynlocalization ma ayseismbe(1iassociatedcally to of 1.5 active cm/yr), with layer pore - the western FromHelikeGPS fault a ndhas historical presentlydata:a low a activity, high probability switched oofff M>6 by newly formedcombiningpressurethehighlastb e strain3faultst w orkme micro-seismic estrainn5 of rate theaThen andtransientsd9offshorewk microseismicitymestern and faults partaseismic (and/oof the deformationrift the is gulfin an sediments) accelerated arestate aseismically of strain deforming at high rate. in the next decades

Shallow water

1.5 cm/yr

PHYLLADES NAPPE ?

Deep DUCTILE LAYER water (from MT) S N

STRAIN MONITORING ARRAYS

S Rayleigh

5.0 x 10-3 bars Pore pressure 1000 s AIG10

-7 Dilatometer 1.0 x 10 strain Trizonia