Jökull - 01.01.2010, Qupperneq 74

Horálek and Fischer
!4
!2
0
2
4
6
8
N
or
th
, k
m
!4 !2 0 2
6
7
8
9
10
11
12
13
East, km
D
ep
th
, k
m
!4 !2 0 2 4 6 8
North, km
1991 1993 1995 1997 1999 2001 2003 2005 2007 2009
0
1
2
3
4
ML
Figure 5. Three perpendicular views of seismicity in the NK zone from 1991 to 2008 (map view – top left,
depth view across the strike – bottom left, depth view along the strike – bottom right) and its magnitude–time
distribution (top right). Colour-coding from blue to red corresponds to the course of seismicity in time. –
Upptakakort jarðskjálfta á Nový Kostel svæðinu 1991–2008. Upptökin eru lituð eftir tíma.
Source mechanisms
It is generally accepted that tectonic earthquakes are
mostly shear slips along a fault and are represented
by the double-couple (DC) force equivalent (assum-
ing a planar fault with isotropic surrounding medium).
However, pressurized fluids or magma may cause rup-
turing during which the slip direction is not parallel
to the fault plane, i.e. shear slip along a fault com-
bined with an opening of the fault (tensile earthquake
according to Vavryc̆uk, 2001). Such process is rep-
resented by a more complex force equivalent, which
is manifested, in addition to the DC, by a significant
74 JÖKULL No. 60