Jökull - 01.01.2005, Page 89

Seismic characteristics of the Hekla volcano
22˚W 21˚W 20˚W 19˚W
63˚ 40'N
64˚ 00'N
64˚ 20'N
0 25 50 km
HAU
SAU LJHE
H T
V
BUR
WVZ
SISZ EVZ
NVZ
TFZ
Figure 1. Index map of the Hekla area and the seismograph network. Black triangles are the digital SIL seis-
mograph stations and grey triangles the analogue stations, those mentioned in the text are named. The black
diamond represents the strain station BUR. The central volcanoes are outlined, their fissure swarms are shaded
grey (Einarsson and Sæmundsson 1987) and the calderas are hatched (Jóhannesson et al. 1990). Named central
volcanoes are: H = Hekla, V = Vatnafjöll, T = Torfajökull. Thick black lines are the faults of the South Iceland
seismic zone. Short dashed lines mark the glaciers. The box with dashed outline shows the study area. Smaller
index map shows the locations of the Western (WVZ), Eastern (EVZ) and Northern (NVZ) volcanic zones, the
South Iceland seismic zone (SISZ), and the Tjörnes fracture zone (TFZ). All the figures are drawn using the
Generic Mapping Tools program (Wessel and Smith 1998). – Yfirlitskort af Suðurlandi og skjálftamælanetinu.
Svartir þríhyrningar tákna mæla í stafræna landsnetinu, gráir þríhyrningar eru hliðrænir mælar, sem skrá með
penna á pappír. Svartur tígull táknar þenslumælinn við Búrfell, BUR. Megineldstöðvar, sprungusveimar og
öskjur eru sýndar. Megineldstöðvarnar Hekla, Vatnafjöll og Torfajökull eru merktar með H, V og T. Þykkar,
svartar línur eru sniðgengi á skjálftabelti Suðurlands. Jöklar eru sýndir með strikalínum og strikalínukassi
afmarkar rannsóknarsvæðið, sem sýnt er nánar á 2. mynd.
strike-slip faults, and events up to magnitude 7.1 have
occurred (Einarsson 1991; Stefánsson et al. 1993).
The earthquakes have a tendency to deepen towards
east: in the westernmost part of the zone they are typ-
ically located in the uppermost 6 km and in east at 6–
12 km depth. The east end of the seismic zone, about
15 km in width, is included in this study of seismicity
in the Hekla area.
THE SEISMIC DATASET
This study is based principally on seismic data gath-
ered by the digital seismic stations of the SIL (South
Iceland Lowland) network (Figure 1), maintained by
the Icelandic Meteorological Office. The SIL net-
work has gathered data since 1990 (Stefánsson et al.
1993). Originally the network consisted of eight digi-
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