Jökull - 01.01.2014, Page 69

Earthquake Sequence 1973–1996 in Bárðarbunga volcano
-2
0
2 May 5, 1994 Z
-2
0
2 R
-2
0
2 T
-1
0
1
Dec. 11, 1995 Z
-1
0
1
R
-1
0
1
T
-2
0
2 Sept. 29, 1996 Z
-2
0
2 R
-2
0
2
0 10 20 30 40 50 60 70 80 90 100 110 120seconds
T
Figure 4. Waveforms of Bárðarbunga earthquakes 1994, 1995, and 1996, recorded by the ICEMELT broadband station
KAF, in SE-Iceland (Figure 1). Two minutes long, 3-component, vertical, radial and transverse (Z, R, T) records are shown
for each event. Note that the amplitude scale is not the same for all records. Some of the surface wave phases of the 1994
and 1996 events are clipped, but the 1996 event is obviously the largest of the three. – Bylgjugögn þriggja meginskjálfta í
Bárðarbungu 1994, 1995, og 1996, frá breiðbandsmæli ICEMELT netsins á Kálfafelli (KAF), Suðausturlandi (sjá 1. mynd).
Tímagluggi er tveggja mínútna langur, og þrír þættir hraðahreyfingar jarðar eru sýndir í lóðrétt- (Z), geisla- (R) og þver-
stefnu (T). Athugið, að skali á bylgjuútslagi (y-ás) er ekki sá sami fyrir skjálftana. Sumar yfirborðsbylgjur skjálftanna frá
1994 og 1996 eru skornar (mælar hafa farið í botn), en 1996 skjálftinn er greinilega stærstur þessara skjálfta.
Table 2. Examples of small and medium size earthquakes in Iceland. – Dæmi um jarðskjálfta á Íslandi.
Date time UT latitude longitude mb MS MW fc,a fc,b obsc region
dags. tími n.l. breidd v.l. lengd Hz Hz
1987 May 25 11:31:54.7 63.909 -19.779 5.8 5.8 5.9 0.50 ±0.1 1 Vatnafjöll1
1994 Feb. 08 03:27:52.1 66.451 -19.249 5.3 5.3 5.5 0.43 ±0.06 3 Skagafjörður2
1994 May 05 05:14:48.6 64.634 -17.430 5.7 5.2 5.4 0.22 ±0.04 3 Bárðarbunga2
1994 Aug. 20 16:40:25.9 64.035 -21.241 4.3 3.2 ±0.3 2 Hengill2
1994 Nov. 18 23:54:03.7 64.508 -17.686 4.2 3.9 1.2 ±0.4 3 Loki Ridge2
1995 Oct. 13 15:14:16.0 64.484 -17.749 4.3 3.9 1.4 ±0.5 4 Loki Ridge2
1995 Nov. 18 01:56:23.9 64.647 -17.419 4.3 0.9 ±0.3 4 Bárðarbunga3
1995 Dec. 11 05:22:46.2 64.671 -17.503 4.9 4.5 0.47 ±0.13 4 Bárðarbunga2
1996 Sept. 29 10:48:17.09 64.666 -17.444 5.3 5.4 5.6 0.17 ±0.03 7 Bárðarbunga4
aP wave corner frequency. bUncertainty of P wave corner frequency. cNumber of observations. Locations from: 1Bjarnason
and Einarsson (1991), 2SIL network, 3PDE of USGS, 4Einarsson et al. (1997). MW are determined by Harvard University,
Cambridge, USA, mb and MS by USGS.
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