Investigation of local very long period seismic signals registered at Mýrdalsjökull glacier, south Iceland
(English)Manuscript (Other academic)
Strong and repeating very long period (vlp) signals (10-30 sec) on and around the western Mýrdalsjökull ice cap, which covers the Katla volcano in South Iceland, are recorded simultaneously with long period (lp) events of magnitude >2. The signals are recorded on 6 broadband and 2 higher frequency three-component seismic stations. The vlp signals are linearly polarized and the horizontal polarization direction points to the same source as the lp events, which have recently been interpreted as being generated by ice falls over an escarpment in a steep outlet glacier. The vlp events are registered on several different instrument types, which implies that they must be due either to a generic problem with the instruments or that they are real signals. They do not appear to be consistent with P-, S- or surface wave behaviour.Similar signals elsewhere have been interpreted as the combined effect of static displacement and tilt caused by ground deformation due to magma movements within a volcano. The three-component data are therefore modelled as the combined effects of tilt and vertical translation caused by the ice movements. Simple deformation modelling shows that the observed vlp signals are inconsistent with the ice fall source in the relative magnitudes of the vertical and radial displacements and, in line with results from elsewhere, the magnitudes of the observed effects are large relative to the model response. Thus the origin of the vlp signals remains enigmatic.Our analysis suggests that it is unlikely that the signal is an instrumental artefact. Possible physical origins are discussed.
Mýrdalsjökull, Katla volcano, seismic tilt, vlp-signals, lp-signals, acceleration, static deformation
Research subject Geophysics Specialized In Seismology
IdentifiersURN: urn:nbn:se:uu:diva-101011OAI: oai:DiVA.org:uu-101011DiVA: diva2:211530