Volcanic Tremor and Low-Frequency Earthquakes in Iceland
Most earthquakes in Iceland are of the usual high-frequency type, reflecting brittle failure of the crust. Earthquakes lacking energy in the higher frequencies (low-frequency earthquakes) also occur, particularly in volcanic regions. Low-frequency earthquakes in the volcanic systems of Iceland span a broad spectrum with respect to amplitude/duration ratios. They often accompany magmatic intrusions or extrusions, and in the cases of Krafla and Hekla, they have been found to correlate in time with the opening of surface fissures. In other cases, such as at SW-Mýrdalsjökull and Torfajökull, low-frequency earthquakes are associated with central volcanoes that have not erupted for centuries. Volcanic tremor has been recorded during all recent eruptions in Iceland. In Krafla, at least two types of tremor have been recorded, one associated with intrusions, the other with eruptions. The two types have distinctly different characteristics, and are produced by different physical processes.
KeywordsAttenuation Brittle Dura Tephra Malone
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