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Fracturing and earthquake activity within the Prestahnúkur fissure swarm in the Western Volcanic Rift Zone of Iceland
Author(s) -
Hjartardóttir Ásta Rut,
Hjaltadóttir Sigurlaug,
Einarsson Páll,
Vogfjörd Kristín,
MuñozCobo Belart Joaquín
Publication year - 2015
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.983
H-Index - 232
eISSN - 2169-9356
pISSN - 2169-9313
DOI - 10.1002/2015jb012341
Subject(s) - geology , dike , lava , fissure , rift , volcano , seismology , rift zone , swarm behaviour , earthquake swarm , graben , geomorphology , petrology , induced seismicity , paleontology , tectonics , mathematical optimization , mathematics
The Prestahnúkur fissure swarm is located within the ultraslowly spreading Western Volcanic Zone in Iceland. The fissure swarm is characterized by normal faults, open fractures, and evidence of subglacial fissure eruptions (tindars). In this study, fractures and faults within the Prestahnúkur fissure swarm were mapped in detail from aerial photographs to determine the extent and activity of the fissure swarm. Earthquakes during the last ~23 years were relocated to map the subsurface fault planes that they delineate. The Prestahnúkur fissure swarm is 40–80 km long and up to ~20 km wide. Most of the areas of the fissure swarm have been glacially eroded, although a part of it is covered by postglacial lava flows. The fissure swarm includes numerous faults with tens of meters vertical offset within the older glacially eroded part, whereas open fractures are found within postglacial lava flows. Comparison of relocated earthquakes and surface fractures indicates that some of the surface fractures have been activated at depth during the last ~23 years, although no dike intrusions have been ongoing. The existence of tindars nevertheless indicates that dike intrusions and rifting events do occur within the Prestahnúkur fissure swarm. The low‐fracture density within postglacial lava flows and low density of postglacial eruptive fissures indicate that rifting episodes occur less often than in the faster spreading Northern Volcanic Zone.