Jökull - 01.12.1984, Side 19

TABLE 1.
Background tremor Tremor bursts
Frequency Fairly constant, Anharmonic.
two main classes The freq. fluctuates
Low freq. tremor <3 Hz between 2 and 5 Hz.
High freq. tremor >3 Hz Usually around 3 Hz.
Amplitude Fairly constant gradually decreasing Unstable
Duration May 28 1200-2000 hrs. <3Hz Total of 83 hours.
May 28 2000-2200 hrs. >3Hz From May 28 at 1453
May 28 2200-2400 hrs. <3Hz May 29 1000-1300 hrs. >3Hz to June 2 at 0138
HAFURSEY MAY 28.1983 12dB
1min
Fig. 4. A part of the seismogram of May 28 1983, from the station HF, at a distance of 120 km from
Grímsvötn, showing events of the earthquake swarm. Note the variable appearance of the earthquak-
es, especially with respect to maximum amplitude and coda length. The seismograph writes one line in
10 minutes. Second and minute marks are recorded.
4. mynd. Hluti skjálftarits 28. maí 1983 úr mœlinum í Hafursey (HF á 1. mynd), sem er í 120 km
fjarlœgð frá Grímsvötnum. Tíu mínútur eru milli lína á ritinu, sekúndu- og mínútumerki eru sýnileg. Sjá
má jarðskjálfta úr hrinunni, sem var undanfari gosuppkomunnar. Takið eftir hversu ólíkir kippirnir eru
hver öðrum í útliti.
JÖKULL 34. ÁR 17