Jökull - 01.12.2003, Side 53

Seismicity in Iceland 2002
Figure 2. Earthquake epicenters within the Tjörnes Fracture Zone during 2002. Red crosses denote earthquakes
from September 16 to October 1. Green stars denote mb > 4 earthquakes. Also shown is the NEIC fault plane
solution for the mainshock and the monthly number of earthquakes during 1994–2002 within this region. –
Kortið sýnir staðsetningar jarðskjálfta í Tjörnesbrotabeltinu 2002. Rauðir krossar eru skjálftar frá 16. septem-
ber til 1. október. Grænar stjörnur tákna mb> 4 skjálftana. Brotlausn aðalskjálftans er einnig sýnd. Línuritið
sýnir fjölda jarðskjálfta á mánuði frá 1994 til 2002 á svæðinu.
The largest Mýrdalsjökull earthquake recorded by
the SIL system, 4.3 (mb), occurred on April 27, 2002
at the northeastern rim of the Mýrdalsjökull (Katla)
caldera.
VATNAJÖKULL
A group of central volcanoes underlies the Vatnajök-
ull ice cap. Geothermal areas within these volca-
noes melt the glacier at the bedrock. The accumu-
lation of meltwater, reaching a critical level, results
in a jökulhlaup (Björnsson, 2002). Jökulhlaups from
Grímsvötn into the river Skeiðará (Skeiðarárhlaups)
occurred in March, April, and May 2002 (Roberts,
2003). Seismic tremor and icequakes were recorded
in Skeiðarárjökull in relation to these jökulhlaups.
Five jökulhlaups from Grænalón into the river Súla
(Súluhlaups) occurred during the second half of the
year (Roberts, 2003). Icequakes in Skeiðarárjökull
were also recorded during the Súluhlaups (Figure 4).
Both Skaftá cauldrons (Skaftárkatlar) drained into
the river Skaftá during the year. A jökulhlaup from
the eastern cauldron occurred in July and the western
cauldron in September. Seismic tremor was recorded
by the nearest SIL stations during these jökulhlaups.
Earthquakes in the vicinity of the Skaftá cauldrons
were also recorded.
JÖKULL No. 53, 2003 51