Portrait of the SNSF Ayim Yılmaz, Head of Division Biology & Medicine.
Seismicity induced by seasonal variation of …...vided by a Swiss National Science Foundation...
Transcript of Seismicity induced by seasonal variation of …...vided by a Swiss National Science Foundation...
Conclusion• The semi-analytical model shows that poroelastic interaction may have indeed caused
changes in CFS. Observed seismicity in positive CFS changes, although the values
are smaller than few decimal of bar. A rate-and-state model is able to predict peaks
of seismicity, while overestimating the rate at later time of observation. Earthquakes
interaction may have played a role in reducing the Coulomb stress.
• The use of a numerical model highlights the importance of accounting for
heterogeneities, which could enahnced and focus the stress variation at observed
seismogenetic region.
This research is funded by a Reasearch agreement between SED and INGV. Funding to A. P. Rinaldi are pro-vided by a Swiss National Science Foundation (SNSF) Ambizione Energy grant (PZENP2_160555).
Easting (km)-10 -5 0 5 10
Nor
thin
g (k
m)
-5
0
5
10
-10
Effect of heterogeneities
WN
Quaternary Mélange Carbonate
Density (kg/m3) 2300 2300 2300
1-30.0 30.0 30.0
Poisson’s ratio
α Biot 0.9
B Skempton
Permeability (m2) 5.10-15
Young’s modulus (GPa)
1.00 1.00 1.00
5.10-15 5.10-17
0.9 0.9
0.25 0.25 0.25
}}}
Quaternary (weak, permeable) 500m thickness
Melange (stiff, low permeable)-500 m to -1800m
Carbonate (stiff, permeable)
OPENGEOSYS simulator
- Lake: time-dependent boundary condition. Vertical load and pore pressure- Open pressure boundary- Fixed displacement boundary- 30 days loading/ protracted response
Easting (km)-10 -5 0 5 10
Nor
thin
g (k
m)
-5
0
5
10
-10
-0.8 -0.4 0 0.4 0.8CFS (bar)
Days
Wate
r le
vel
Focal plane: 330, 60, -80
Focal plane: 120, 30, -120
Days
Wate
r le
vel
Easting (km)-10 -5 0 5 10
Nor
thin
g (k
m)
-5
0
5
10
-10
Coulomb and Rate-and-State: homogeneous model
-0.8 -0.4 0 0.4 0.8CFS (bar)
-8 -4Easting (km)
-15
-10
-5
0
Nor
thin
g (k
m)
2003
0 84
4 km depth (seismicity between 2 km and 4 km)
6 km depth (seismicity between 4 km and 6 km)
-8 -4Easting (km)
-15
-10
-5
0
Nor
thin
g (k
m)
2009
0 84-8 -4Easting (km)
-15
-10
-5
0
Nor
thin
g (k
m)
1967
0 84
-8 -4Easting (km)
-15
-10
-5
0
Nor
thin
g (k
m)
2003
0 84 -8 -4Easting (km)
-15
-10
-5
0
Nor
thin
g (k
m)
2009
0 84-8 -4Easting (km)
-15
-10
-5
0
Nor
thin
g (k
m)
1967
0 84
1972 19921982 2002 2012
initial �lling
440
480
520
time (year)
wat
er lev
el (
m.a
.s.l.)
Rate-and-State
SEMI-ANALYTICAL MODEL
- Poroelastic model to compute changes in loading and pressure diffusion due to water level changes- Resulting CFS changes are inputed to a Rate-and-State model to compute seismicity rate (for fault oriented similar to observation - Valoroso et al., 2009)
Diffusivity (m2/s) 0.05
0.5
Poisson’s ratio
Friction 0.6
B Skempton
0.25
50
60
70
80
90
Wat
er le
vel (
m)
0 1 3 5 7
Time (years from 01/01/2001)
0
0.05
0.10
0.15
Rm
od (#
ev/v
olum
e)
0 2 4 6 80
2
4
6
Rob
s (#e
v/vo
lum
e)
2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013
modelledobserved
0.20
9 1110 12
100
8
0.0009
1280.7
0.058
Aσ (MPa)
ta (days)
r (#/day)
Rate-and-State
Conceptual model
Days
Wate
r le
vel
DaysPre
ssure
Days
Pre
ssure
Hydraulic effectThe bottom of the lake
is pressurized by water co-lumn weigth: no volumetric strains, pressure evolution depends on permeability k
and specific storage Se
Mechanical effectThe bottom of the lake
is deformed by water-co-lumn weigth: volumetric and shear strains genera-te the pressure evolution, which depends on perme-ability k and specific sto-rage Se, as well as on po-
roelastic properties.
M to H coupling effectAdditional pressure response
Additional stress changes
H to M effectTime dependent
DCFSMitigate pore pressure drop
Effective stre
ss re
duction
Undra
ined
resp
onse
Introduction
A water reservoir affects the underlying crust
stress state through the poroelastic response
to the weight of the water volume stored and
by the consequent fluid movement.
The artificial lake of Pertusillo in Val d’Agri
(Italy) is one of the known water reservoirs
showing protracted seismic activity for several
years after the initial filling in 1963. More than
800 small magnitude events (ML <3; Mc=1.1)
were located between 2001 and 2013 by a
monitoring network of a local industry operator
supplemented by permanent and temporary
stations of the Istituto Nazionale di Geofisica
e Vulcanologia. Hypocenters concentrate at
a shallow depth (< 5 km) to the south of the
lake. During the same period the reservoir
water level fluctuated in average of tens of
meters between summer and winter periods.
The observed seismicity rate positively
correlates with these seasonal oscillations.
15.8˚ 15.9˚ 16˚ 16.1˚
40.2˚
40.3˚
3 km
2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013Year
Lat.
Long.
CM2
Dam
Figures from
Valoroso et al. (2009)
Seismicity induced by seasonal variation of reservoir level: the case of Pertusillo lake, Val D’Agri (Italy)Rinaldi A. P.(1), Catalli F.(2), Urpi L.(1), Improta L.(3), Buttinelli M.(3)
(1) Swiss Seismological Service, ETH Zürich, Switzerland; (2) Deutsches GeoForschung- Zentrum, GFZ – Potsdam, Germany; (3) Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Roma, Italy