Jökull - 01.01.2005, Blaðsíða 108

Sigurlaug Hjaltadóttir et al.
RR
RP SISZ
M
Vatnajökull
TFZ
Mlw=4.2
Mlw=4.5
Mlw=3.9
mb=4.5
−24˚ −22˚ −20˚ −18˚ −16˚ −14˚
64˚
65˚
66˚
67˚
Mlw 0 1 2 3 4 5 6
LEGEND
Earthquakes 2004
Volcanic system
(Einarsson and Sæmundsson, 1987)
Fissure swarm
Central volcano
Caldera
Fissures and faults
L
B
G
S
K
A
Figure 1. Seismicity in Iceland in 2004. Earthquake epicenters are only plotted for events recorded at at least
five stations and with Mlw ≥0. Main tectonic features are shown. RR denotes the Reykjanes Ridge, RP the
Reykjanes Peninsula, SISZ the South Iceland Seismic Zone, WVZ the Western Volcanic Zone, TFZ the Tjörnes
Fracture Zone, M the Mýrdalsjökull ice cap, L Lokahryggur, G Grímsvötn, S Skeiðarárjökull, B Bárðarbunga
and K Kaldbakur. Black triangles denote SIL-stations. – Jarðskjálftavirkni á Íslandi 2004. Skjálftamiðjur
eru einungis teiknaðar fyrir skjálfta sem mældust á að minnsta kosti fimm stöðvum og með M lw ≥0. Svartir
þríhyrningar tákna SIL-stöðvar.
of the Vatnajökull ice cap (Jakobsdóttir et al., 2005).
These stations are sited near to the reservoir of a hy-
droelectric plant and they are intended for monitor-
ing seismicity induced by the filling of the reservoir.
Additionally, the stations have lowered the detection
threshold of the SIL system for earthquakes beneath
northwest Vatnajökull and the Askja caldera.
SEISMIC ACTIVITY
Over 12,000 earthquakes were detected during 2004;
this figure is similar to the yearly number of events
recorded between 2001 and 2003 (Þorbjarnardóttir
and Guðmundsson, 2003; Þorbjarnardóttir et al.,
2003; Guðmundsson et al., 2004). Likewise, the total
108 JÖKULL No. 55