Atmospheric pressure gradient as
a possible trigger of great earthquakes
Bondur V.G., Garagash I.A., Gokhberg M.B., Grekhova E.A.,
Kolosnitsyn N.I., Shalimov S.L., Veys V.A.

Possible Trigger Mechanisms
• Seismic wave action
M. West, J.J. Sanchez, S.R. McNutt. Science, vol. 308, 1144 (2005)
• Electromagnetic action – MGD pulses and Geomagnetic storms
1) E.P. Velikhov, Theory and method of deep electromagnetic sounding
of crystalline shields. Apatity, 2006
2) N.T. Tarasov et al. USSR Doklady, vol. 353, 545 (1997); Volcanology
and Seismology, 4-5, 153(1999);
3) G.A. Sobolev et.al. Volcanology and Seismology, 3, 63 (2004)
• Atmosphere pressure gradient (APG)
A.D. Sytinsky, USSR Doklady, vol. 245, 1337 (1979);
V.G. Bondur, I.A. Garagash, M.B. Gokhberg et al. Doklady Ac.Si., vol.
430, 400-404 (2007)

2 .3 1 5
4
0
x z(  )
kPa, cm
Rayleigh wave reconstruction:
shear stress on depth 2 km –
σxz = 1.95 kPa;
amplitude uz = 0.75 cm;
velocity
U = 3.7 km·s-1;
period
T = 30 s;
wave length λ = UT = 111km;
decay depth for longitudinal (Ll)
and transverse (Lt) components:
Ll = 21 km, Lt =45 km
G = 3.5·1010 Pa
360
2
zz(  )
x x(  )
10
0
u z(  )
2
 2 .3 1 5
4
0
0
90
180

p h ase
270
360
360
When σxz achieves maximum the values σxz, σxz, uz = 0
and local earthquakes are occured
Energy density F = (1/4)( σxz)2/G
Full energy
E = F·V
Sadovsky formula: lg EL =lgV + 2
EL = 4.47·1014 erg (M = 1.9)
V = 4.5·105 m3
Energy relation
Seismic records of the Sumatra earthquake and local events
at Mount Wrangell
E = 1.3·108 erg
E/EL ~ 10-6

Electromagnetic Trigger Mechanisms
• Central Asian (70-80): N. Tarasov et al. Earth crust investigation by
means of electric dipole with energy impulse Eem ≈ 1014 erg. As a
result seismic activity was recorded with seismic energy Esm ≈ 1019
erg so that the energy ratio is Eem/ Esm ~ 10-5
• G.A. Sobolev et al. showed that due to trigger mechanism of
geomagnetic storms with sudden commencement the appearance of
earthquakes with M > 2 in some events may be explained (G.A.
Sobolev et al. Volcanology and Seismology 2001, № 11, 62-72;
2004, № 3, 63-75; Fizika Zemli 2002, № 4,3-15).
• Following E.R. Mustel et al. (Astron. J., vol. 42, 1232 (1965))
geomagnetic storm time variations can globally excite multiple
regions with atmospheric pressure gradients. This results in
increase of a chance to get by atmospheric gradient of a region with
preparing EQs

Trigger Mechanism by APG
• The estimation of the trigger effect from APG is making
on example of the biggest earthquake Sumatra M = 9.1
• Due to “inverse barometer” effect the deformations are
confined only by Sumatra area S= 1000×200 km2.
• At pressure difference p = 1.33·103 Pa (10 mm Hg), the
shear
• modulus – μ, Lame’s parameter – λ: μ = λ = 35·109 Pa
and Poisson ratio σ = 0,25, using Boussinesq solution
for deformation energy it has obtained the estimate
– E ~ 3·1019 erg
• Magnitude M = 9 correspond to energy EL of 2·1025 erg
• As a result
– E/EL ~ 10-6

The pressure p created by atmospheric anomalies get in deeply and unlike seismic perturbations operate long
enough within several days1. Distribution of main shear stress t arising in elastic earth crust under
the influence of atmospheric anomaly is shown.
Distribution of dimensionless
main shear stress t/p
Distribution of the relation of
horizontal deformation ex/e to
characteristic deformation e=p/2G
Distribution of the relation of
vertical deformation ey/e to
characteristic deformation e=p/2G
1Garagash
I.A., Ingel L.Kh. and Yaroshevich M.I. (2004) A Possible Mechanism of Atmospheric Effects on Seismic Activity near Ocean Coasts, Izvestiya, Phys. Solid
Earth 40, p.692–698

R is parameter of closeness of stress state to strength limit
The parameter R entered by us allows to watch for dynamics of stress state
 1*   1   1
R(
 3*   3   3
 1   3  1   3

sin  )
2
2
 1   2   3 are the main stresses
 is the friction angle
,  are the shear stress intensity and shear strain intensity, respectively
t s is the maximum strength value
t k is the residual strength

3D Calculation of the stress-strain state on the Californian testing area “China Lake” with evidence
of short-term earthquake prediction
Fault zones close to Coulomb-Mohr shear zone yields proper
condition due to decreasing of atmospheric pressure by 2.5%
range z -3200m -4800m
1.
pmax  2500Pa
range z -4800m -6400m
Gokhberg M.B.,Garagash I.A.,Nechaev Yu.V.,Rogozhin E.A., Yunga S.L. Geomechanical model of seismic claster China Lake, South California Researches in the
geophysics. IPE RAS, 2004

Examples of the APG before EQ with M > 7.5
in the epicenter vicinity
gPa
Alaska 2003 M = 7.8
1045
773
mm Hg
763
753
↑↑
↑
743
758
↑
-30 -25 -20 -15 -10 -5
1014
New Guinea 2005 M = 7.7
gPa
1016
0
↑↑↑↑ ↑
985
0
0
5
5
Philippines 2002 M = 7.5
1018
Indonesia 2002 M = 7.6
gPa
Tonga 2006 M = 8
mm Hg
758
↑
-30 -25 -20 -15 -10 -5
-30 -25 -20 -15 -10 -5
1014
1010
↑ ↑ ↑
754
5
gPa
1012
∆
5
1005
∆
∆
0
1015
995
5 5
5
-30 -25 -20 -15 -10 -5
1025
762
∆
1000
1035
766
1004
↑
China 2008 M = 7.9
774
mm Hg
770
∆
1008
∆ ∆ ∆ ∆∆
Kuril islands 2006 M = 8.3
∆
Banda sea 2006 M = 7.6
gPa
1014
1012
∆
∆
∆
∆
∆∆ ∆
∆
Sea of Okhotsk 2008 M = 7.7
-30 -25 -20 -15 -10 -5
0
750
5
^↑ ^
↑^
↑ ↑ ↑
-30 -25 -20 -15 -10 -5
Koryakia 2006 M= 7.6
775
mm Hg
765
1006
0
↑
↑
-30 -25 -20 -15 -10 -5
5
Samoa 2009 M = 8.1
762
↑
∆
5
↑
↑
1008
- 32
6 7.5
∆
6
∆
0
-33
∆
-30 -25 -20 -15 -10 -5
765
mm Hg
1010
↑ ↑↑ ↑
↑
1006
1010
754
- 92
1008
gPa
0
5
Tonga 2009 M = 7.6
1014
mm Hg
760
755
∆
↑
∆
-30 -25 -20 -15 -10 -5
735
0
5
^
↑
5
^
∆
750
↑
745
1010
7
^↑ ↑
-30 -25 -20 -15 -10 -5
0
↑
∆
-38
758
- 34
6.5
∆
755
5
754
↑
-30 -25 -20 -15 -10 -5
1006
0
5
-30 -25 -20 -15 -10 -5
Days (relative to an earthquake moment)
Only negative APG before EQ can produce trigger effect

0
5
Atmospheric pressure
mm Hg
mm Hg
New Zealand 2009 M = 7.9
770
Chili 2005 M = 7.8
761
760
750
757
740
-30
1035
-25
-20
-15
-10
-5
0
5
Scotia Sea 2003 M = 7.6
gPa
753
1025
-30
-25
-20
-15
-10
-5
0
1015
1005
-30
-25
mm Hg
-20
-15
-10
-5
0
5
Macquarie island 2004 M = 8.1
770
760
750
740
-30
-25
-20
-15
-10
-5
0
5
Days (relative to an earthquake moment)

5
APG statistical distribution
relatively time before earthquakes
2000 – 2010 years. The number of events N ~ 50

Modeling of APG trigger for Sumatra M9.1
While seismic and electromagnetic impulses last seconds, and the sources of large earthquakes has the inertial action, the APG continue
during the days and its scale is comparable with the scale of large earthquakes
If parameter R < 0 the earth crust keeps away from a limiting state, at R> 0 – it comes nearer. In calculations the transfer of pressure upon
the earth crust is carried out only on areas which have been not covered with ocean. The maximum value of pressure excess is no more than
1% from the average atmospheric pressure. It is evident that in the anomalous zone the top layer 1 keeps away from the strength limit
whereas the deeper layers 2, 3 and 4 – comes nearer. Thus, abnormal pressure approaches these zones to strength limit and hence can cause
trigger effect.
Distribution of parameter R in the layer 1
1.The four-layer model has been designed for Sumatra
2. 3D distribution of the elastic energy density was calculated
3. Dynamic of parameter R induced by APG is presented
Distribution of parameter R in the layer 4
Bondur V.G., Garagash I.A., Gokhberg M.B., Lapshin V.M., Nechaev Yu.V., Steblov G.M., Shalimov S.L., (2007) Geomechanical models and ionospheric
variations related to strongest earthquakes and weak influence of atmospheric pressure gradients. Doklady Earth Sciences, Vol. 414, No. 4, pp. 666–669

Conclusion
• For all trigger mechanism the ratio between input and
output energies is estimated to be 10-5 – 10-6
• Large scale atmospheric pressure gradient (APG) can
create the additional deformation deep enough in the
earth’s crust
• The ocean – land boundary can effectively transform
homogeneous atmospheric pressure into its sharp
gradient acting on the earth’s crust
• APG is large scale process that can be considered as
the trigger mechanism for strongest earthquakes

For discussion
APG trigger conception
can kill
the representation of the existence different
precursor’s effects
APG and magnetic storms exist permanently.
These phenomena with very well known physics produce a lot
of different anomaly in the Earth-Atmosphere-IonosphereMagnetosphere systems which can be mistakenly considered
as the precursor effects.

Monitoring of strain and strength of earth crust on the basis of close to real geomechanical models
for the purpose of the seismicity forecast on the interval week – month.
Model of earth crust of Southern California: a) general view,
b) normalized distribution of the damage in the upper crust
and c) map GPS velocities
Changes of summary magnitudes
Normalized distribution of parameter R of nearness of stress state
to strength limit for 15.12.2009 in the layer 1 (upper crust)
and in the layer 4 (middle crust)
(the dark blue graph) and strength parameter R in the upper crust (the red graph)
M

Distribution of the relation of horizontal
deformation ex/e to characteristic
deformation e=p/2G
Distribution of the relation of vertical
deformation ey/e to characteristic
deformation e=p/2G
