Náttúrufræðingurinn - 1986, Page 10

Sigurður Þórarinsson. 1949. Um aldur
Geysis. - Náttúrufr. 19: 34-41.
Sigurður Þórarinsson. 1958. Jarðskjálfta-
kort Eysteins Tryggvasonar með hlið-
sjón af því sem vitað er um jarðskjálfta
á fslandi af sögulegum heimildum. - í:
Greinargerð jarðskjálftanefndar um
jarðskjálftahættu á íslandi (höf.
Eysteinn Tryggvason, Sigurður Thor-
oddsen og Sigurður Þórarinsson).
Tímarit V.F.Í. 43: 81-97.
Sigurður Þórarinsson. 1967. The eruption
of Hekla in historical times. - The
Eruption of Hekla 1947-1948 I: 1-
170. Vísindafélag íslendinga.
SUMMARY
An ancient earthquake fracture
at Holt, Biskupstungur, South
Iceland
by
Haukur Jóhannesson
and
Bryndís G. Róbertsdóttir
Icelandic Museum of Natural History
P.O. Box 5320
Reykjavík
An ancient earthquake fracture at Holt
in Biskupstungur, South Iceland (Fig. 1) is
described. It consists of three short en
echelon fractures with an overall trend of
N20°E and individual trends N32°E to
N56°E. The fractures are covered by soil
and are exposed as pits and elongated
furrows (Fig. 3). The fracture seems to be
related to the Vatnsleysa fault (Fig. 2) and
may have been formed as a result of a
Storm, G. 1888. Islandske Annaler intil
1578. — Christiania: 667 s.
Sunnlenskar byggðir. 1980. 1. bindi. Tung-
ur, Hreppar, Skeið. Búnaðarsamband
Suðurlands, Reykjavík: 520 s.
Sveinbjörn Björnsson. 1975. Jarðskjálftar
á íslandi. — Náttúrufr. 45: 110—133.
Sveinbjörn Björnsson. 1978. sjá Almanna-
varnir 1978.
Trausti Einarsson. 1938. Geysir í Hauka-
dal. — Tímarit V.F.Í. 23: 53—56.
Þorvaldur Thoroddsen. 1899—1905.
Landskjálftar á íslandi. — Hið íslenzka
bókmentafélag, Kaupmannahöfn: 269 s.
strike-slip movement along it (Fig. 4).
The age of the Holt fracture is uncert-
ain. A minor movement of the fracture
was observed in the 1896 earthquake.
There are ruins of farmhouses on the edge
of the fracture. It has been suggested that
the farm (named Holt or Útholt) was
abandoned in the course of rifting of the
fracture and rebuilt about 1200 m further
east and renamed Holtakot. No literary
sources mention this event but from writt-
en accounts it is obvious that the Holtakot
farm has existed since early in the seven-
teenth century. The changing of the farm
site thus happened before 1600.
In the course of a great earthquake in
the year 1294 considerable changes occur-
red at the Geysir thermal field, which is a
short distance north of Holt. It has also
been suggested that the Great Geysir was
formed during that earthquake. It is possi-
ble that rifting may have taken place along
the Holt fracture during the 1294 earth-
quake.
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