Pascal BernardInstitut de Physique du Globe de Paris, France

Fault Mechanics and

Seismic Hazard in the

Rift of Corinth, Greece

and the Corinth Rift Laboratory (CRL) group

CORINTH RIFT

Seismicity 1965-2000 - M>5

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 institutionsCORSEIS, 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

Aigion fault

Helike fault

Mamoussia fault

W E

Helike Fault scarp

Aigion Fault scarp

Aigion City

E W

Dip: 60°

N

E

Helike Fault scarp

AIGION FAULT SCARP

AIG10 BOREHOLE

1000 m

N

conglomerate

limestone

Z=1000 m

Dip: 60° soft sediments

Rigo, 1996; Lemeur, 1999

SOUTH NORTH

Seismicity July-August 1991

- listric normal faults ?

- detachment ?

Aigion

z

M=6.2

M=5.8

M=5.3

DIP ANGLE:

30-35°

Targetarea

SOFT SOIL

AMPLIFICATION

Soft Soil Accelerometric Array

CORSSA

Pitilakis et al., 2004

Z=0 m

14 m

31 m

57 m

178 m

M=3.5, D=13 km

surface14m31m57m

2

5 Spectral Amplification

reference: Z=178 m

Pitilakis et al., 2003

0,00

0,05

0,10

0,15

0,20

0,25

0,30

0,35

0,40

0,45

0,50

0,00 0,05 0,10 0,15 0,20 0,25 0,30 0,35 0,40 0,45 0,50

PGA be droc k (g)

PG

A s

urfa

ce (g

)

Tp = 0.1sTp = 0.3sTp = 0.5sdiagw nios14L-0.1g14L-0.2g14L-0.3g14L-0.4g14L-0.5g14T-0.1g14T-0.2g14T-0.3g14T-0.4g14T-0.5gArg83Sep99Dec14LDec14TRick15

Normalize d acce le ration re sponse spe ctra a t the surface (input De c14T)

0

1

2

3

4

0 0,5 1 1,5 2 2,5 3

Pe riod (s )

PS

A/P

GA

PGA=0.1g

PGA=0.2g

PGA=0.3g

PGA=0.4g

PGA=0.5g

ΕΑΚ2000-Γ

0.5 gPGA bedrock – 180 m

ComputedPGA surface

Design spectra of the Hellenic code

Bedrock Input:

Aigion 1995 record, M=6.2

0.5 g

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

LOCKED

SLIPPING

WEST

CENTER

EAST

Bernard et al., 2004

W

N

Z

Silent creep

High seismicity rate

« Brittle » creep

Low seismicity rate

Locked and aseismic

Bernard et al., 2004

Briole et al., 2001

Modelling of the GPS data – 1990-2000

LOCKED

1.5 cm/yr

SOUTH NORTH

Briole et al., 2001

1.0-1.5 cm/yr

1.0 -1.5 cm/yr

mm/yr

Latorre, 2004

S N

Phyllade nappe ?

18611888

1817

120 years : slip 1.80 m

>250 years : slip > 4.5 mrecent strain acceleration

aseismic strain release

TRANSIENT PROCESSES

SPRING 2001 SEISMIC SWARM

Lyon-Caen et al., 2003

17-23 January 2004 - seismic swarm

HelikeAigion

Aigion

Helike

Bouin et al., 2004

Continuous GPS

2 cm

2003 2004

Briole et 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

4x10-7

24 h

2 h

30 s

Earthquake

M=3.5

2 hBernard et al., 2004

2002

M

2

3

Aseismic strain:

Equivalent source

moment magnitude:

M = 5 +- 0.5

SEISMIC SWARM

Max: M=3.5

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)

Cornet et al., 2004

dip60°

Moretti et al., 2004

24 h0.01 BarRECORD 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

- active faults are dipping 60° and rooting in a seismically active layer between 5 and 9km

- this layer slips at a velocity close to the loading velocity (1 to 1.5 cm/yr), combining micro-seismic and aseismic deformation- the Phyllade Nappe may be a candidate for the localization of

high strain rate and microseismicity- some seismic swarms and moderate earthquakes may be associated with pore pressure or strain transients- the western Helike fault has presently a low activity, switched off by newly formed faults the last 3 km of the offshore faults (and/or the gulf sediments) are aseismically deforming at high rate.

The western part of the rift is in an accelerated state of strainFrom GPS and historical data: a high probability of M>6

in the next decades

DUCTILE LAYER (from MT)

Deep water

PHYLLADES

NAPPE ?

S N

Shallowwater

1.5 cm/yr

STRAIN MONITORING ARRAYS

5.0 x 10-3 bars

1.0 x 10-7 strain

1000 s

Rayleigh

P

Pore pressure AIG10

Dilatometer Trizonia

S