| Abstract |
The Reykjanes Peninsula, Iceland, could soon see a once-in-a-millennium eruption, based on its current unrest and its historical record. This period of volcano-tectonic events threatens nearby airfields, geothermal power plants, and the capital, Reykjavik, where two thirds of Iceland’s population reside. The main sources of risk are lava, volcanic ash, and M greater than 6 earthquakes on large strike-slip faults. Six such known faults lie between 15-35 km from the capital. Here, we investigate whether such large earthquakes and/or an eruption are likely, based on the seismicity seen so far. To do so, we look for specific seismicity patterns indicative of magmatically-induced deformation, and compare seismicity overviews of the current unrest, previous decades, and swarm activity in the 1970s. We identify several cascades of boundary movements in both the current unrest and the 1970s activity, that have neighboring segments activate from east to west along the peninsula. This direction is reversed during the current unrest in a slower cascade, which ended with a ~50 km long boundary segment moving. Based on this and other observations, we suggest that magma intrusion has accelerated boundary deformation significantly. We identify another pattern, where seismicity and surface deformation in Svartsengi, the most seismically active region during this period, is greatly reduced when this activity swaps to the neighboring Reykjanes system. We suggest magma intrusion is halted in one volcanic system, in favor of intrusion in another, and describe several possible mechanisms. We further describe possible scenarios, and their likelihood, for the evolution of the current unrest, which range from a rapid return to quiescence, to full-scale eruption. Whichever scenario occurs, M greater than 6 earthquakes on known faults near Reykjavik are likely. |