Náttúrufræðingurinn - 1954, Side 12

6
NÁTTÚRUFRÆÐINGURINN
Mestu (stærstu) jarðskjálftar, sem mælzt hafa síðan 1904:
31.janúar 1906 í Columbia, S.-Ameríku, stærð 8.6,
15. ágúst 1950 í Indlandi, stærð 8.6.
Mestu jarðskjálftar á Islandi síðan um aldamót:
22. janúar 1910 á Norðurlandi, stærð 7.1,
6. maí 1912 við Heklu, stærð 7.0.
Mestu jarðskjálftar á Islandi síðan jarðskjálftamælingar hófust á
vegum veðurstofunnar:
23. júlí 1929 nálægt Reykjavík, stærð 6%,
2. júní 1934 við Dalvík, stærð 6^/4,
9. okt. 1935 á Hellisheiði og Ölfusi, stærð 6.
Jarðskjálftar af stærðinni 6 geta valdið miklu tjóni á byggingum
á litlu svæði næst upptökunum.
Jarðskjálftar af stærðinni 4% valda einstaka sinnum smávegis tjóni.
Minnstu jarðskjálftar, sem menn finna, eru um 2 að stærð, en
nákvæmustu jarðskjálftamælar geta mælt jarðskjálfta, sem em ná-
lægt 0 að stærð.
SUMMARY:
Earthqiuikes in Iceland 1953 by Eysteinn Tryggvason.
The seismic activity was relatively low in Iceland during this year. No large
shock occurred, and no damage was done by earthquakes.
The largest shock came on February 10th, with epicenter off the north coast
(about 66°40'N, 17“0'W), origin time 14h26m51s GMT, and instrumental magni-
tude about 4%.. This shock was felt over a wide area, up to a distance of about
150 km from the epicenter, but the intensity was low, maximum IY degrees (Modi-
fied Mercalli Intensity Scale of 1931).
On August 20th to 22nd came a swarm of small shocks originating at Mt Heng-
ill (about 64°05'N, 21°16'W). The largest shock of this swarm, at 13hllm on 20th
was felt at Reykjavík (30—35 km distance), and in Hveragerði and Hveradalir
many shocks were felt with the maximum intensity of about V degrees. In Reykja-
vík, the seismometers recorded more than 120 shocks during this swarm.
Earthquakes were felt on 14 days during the year, and sometimes more than
one shock were felt on the same day. On seven days, earthquakes were felt in
Southwest-Iceland, six days in North- or Northeast-Iceland, and one small shock
(somewhat doubtful) was felt in Northwest-Iceland.