Jarðskjálftar á Íslandi

Larger earthquakes in Iceland occur mainly in two zones, a narrow E-W trending zone in S-Iceland and 75 km broad zone off the northern coast. Destruction and ground displacement due to the earthquake sequences of J784 (Ms 7.5-8), 1896 Mg 7-7.5) and 1912 (Ms 7) are described. Considerable seismic activity is observed within the active volcanic zones. The earthquakes occur mainly as swarms of magnitude less than Ms 5. Volcanic eruptions are generally preceded by swarms of earthquakes. Examples of such premonitory earthquakes are given for the eruption of Heimaey 1973, Katla 1625, Lakagígar 1783, Mývatn Fires 1724-1729, Askja and Sveinagjá 1875

Relative locations of earthquakes in the Tjörnes Fracture Zone

The seismicity of the Tjörnes Fracture Zone is distributed over a zone 150 km long and 80 km wide. Teleseismic locations of earthquakes within this zone show a diffuse pattern of epicenters that does not easily lend itself to tectonic interpretation. An attempt was made to locate the earthquakes of 1968 and 1969 relative to one reference earthquake by using relative P-wave arrival times at a fixed set of stations. To ensure consistent picking of the arrival times at a given station, the P-wave signals were correlated visually with the P-wave of the reference earthquake. This method of analysis reduces the errors in the locations caused by source or station irregularities and mis-picking of arrival times of small earthquakes. The method further reduces the scatter of the epicenters introduced by using different sets of stations to locate different earthquakes. The relocated epicenters appear to define a narrow seismic zone, possibly a fault. with a WNW trend. The absolute location of this proposed fault cannot be accurately determined, but most probably it passes within a few kilometers of the island of Grímsey. A focal mechanism solution of one of the earthquakes shows strike-slip motion along the fault in a right-lateral sense. The sense of motion and the strike of the fault is therefore similar to that of the Húsavík Fault about 40 km to the south. Some significant seismic activity is known to have occurred close to, but distinctly off these two faults, notably the magnitude 6 1/4 earthquake that caused extensive damage in the village of Dalvík in 1934. It is suggested that the Dalvík earthquake occurred on a fault parallel to the Húsavík Fault, but 30 km to the south. The transform motion between the submarine Kolbeinsey Ridge and the volcanic zone in northern Iceland is thus demonstrated to occur along two, and possibly three or more parallel strike-slip faults.Peer reviewe

Earthquakes in Iceland during the years 1956, 1957 and 1958

During this period, three seismograph stations were operated in Iceland, at Reykjavík, Akureyri and Vík. A new seismograph station was erected at Kirkjubæjarklaustur (Síða) in 1958, where one vertical Willmore seismograph is operated. The seismic activity in South Iceland was rather low during these years, but higher activity was observed in North Iceland. Earthquakes were felt in Iceland on 6 days during 1956, II days during ]957 and 9 days during 1958. The most pronounced felt earthquakes occurred as follows: 1956. June lst. in Southwest Iceland, maximum intensity VI, radius of perceptibility about 70 km. Ociober 29th in North Iceland, maximum intensity V, radius of perceptibility about 200 km. Epicenter off the coast. 1958. September 27th in North Iceland, maximum intensity VI, radius of perceptibility about 80 km. Desember 6th in North Iceland, maximum intensity IV, radius of perceptibility about 100 km. Epicenter off the coast. After the foundation of the seismograph stations at Akureyri, Vík, and Kirkjubæjarklaustur, the epicentre of Icelandic earthquakes can be determined with some accuracy. The epicentres seem to lie in severai smali regions, where some are known by frequent felt earthquakes, but other were unknown until recently. Two of these previously unknown epicentral regions have been very active in recent years, one in northwestern Vatnajökull (64.4°—64.8°N, 16.5°—18°W), and another around Torfajökull (63.7°-64.0°N, 19.0°-19.5°W). Some 25-30% of all Icelandic earthquakes during the period 1954 to 1958 have occurred in the first of these regions, and about 10% in the second region

Earthquakes in Iceland during 1954 and 1955

The seismograph station at Reykjavik was operated with three short period Sprengnether seismographs during these years. New stations were erected at Akureyri (65°40.3' N, 18°06.0' W) and at Vík (63°25.3' N, 19°01.0' W). At both these stations, one Mainka seismograph is operated, static magnification about 70. The seismic activity in Iceland was rather high during these years, especially during the period September 1954 to May 1955. At Reykjavík about 500 tremors were recorded during 1954 and about 365 during 1955. Of these, about 350 in 1954 and 300 in 1955 were of local origin, epicentral distance less than 500 km. At Akureyri about 90 earthquakes were recorded during 1954 and about 70 during 1955. Earthquakes were felt on at least 21 days during 1954, three days in Northlceland and 18 days in Southwest-Iceland. During 1955 earthquakes were felt on at least 37 days, 24 days in North-Iceland and 15 days in Southwest- Iceland. The most pronounced earthquakes occurred as follows: 1954. September 15th. About 10 shocks were felt at Grindavík. October 29th. Numerous shocks felt at Hveragerði and Hveradalir. The largest shocks were felt over area of about 7000 km-. October 30th. One shock felt over the same area as on October 29th. November 21st. Several earthquakes felt at Hveragerði and Hveradalir. Largest shocks felt over the same area as on October 29th. 1955. January 15th. Considerable earthquakes at Grindavík. Macroseismic area of the largest shocks about 30000 km2. January 18th. Earthquakes felt over 8000 km- area in South-Iceland. February 27th. Strong earthquakes in Axarfjörður, North-Iceland, where tremors were felt on almost all days untill March 20th. Macroseismic area of the largest shocks about 30000 km2. In the epicentral area about 200 shocks were felt during this swarm, the maximum intensity beeing VII on modified Mercalli scale. Minor damage was done in the epicentral region. March 13lh. Strong earthquake in South-Iceland, felt over 10000 km2. April lsl. Strong earthquakes at Hveragerði, where minor damage was done. The intensity of the largest shock was VII—VIII in the epicentral region, and macroseismic area about 60000 km2. This was the largest shock occurring in Iceland during the years covered by this report, instrumental magnitude about 5i/£. May 19th. Earthquake felt over large area in North-Iceland, maximum intensity about V and macroseimic area about 60000 km2. The epicenter was situated off the north coast, east of Grímsey

Earthquakes in Iceland 1953

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 l ^ e ^ S l 8 GMT, and instrumental magnitude 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 IV degrees (Modified Mercalli Intensity Scale of 1931). On August 20t h to 22nd came a swarm of small shocks originating at Mt Hengill (about 64°05'N,21°16'W). The largest shock of this swarm, at 13Mlm 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 Reykjavík, 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

Die Behandlung der Mundschleimhauttuberkulose

Inaugural-Dissertation zur Erlangung der Würde eines Doktors der Zahnheilkunde der Hohen Medizinischen Fakultät der Universität Köl