Intraplate Seismicity in India and Norway: Distribution, properties and causes (IPSIN)

Informations

Funding country

Norway

Acronym

-

URL

-

Start date

1/1/2016

End date

12/31/2022

Budget

714,261 EUR

Fundings

Abstract

IPSIN is a collaborative project between India and Norway to study and compare earthquakes in the two countries. Both India and Norway are affected by so-called intraplate earthquakes that occur away from the plate boundaries. As intraplate earthquakes pose a significant hazard to both countries, they present a unique opportunity to exchange scientific problems and knowledge. Despite being located away from tectonic plate boundaries, small to moderate magnitude earthquakes occur in Nordland, Northern Norway, especially along the coast and the edge of the continental shelf. Seismic swarms - earthquakes that cluster in time and space without being associated with a dominant main shock - are common in this region. The seismicity of Nordland has been monitored for decades, but its causal process is still debated. We investigated the origin of this seismicity by using earthquake signals to image the seismic velocity structure of the subsurface beneath Nordland. The images show two main features: a fractured and fluid-filled upper crust in the vicinity of seismic swarms, and a Moho step that runs parallel to the coast, beneath the seismically active corridor of Nordland. As a complementary analysis, we infer the earthquake faulting types by looking at how the earthquakes' waves radiate. We find that the coastal earthquakes are dominated by normal faulting events caused by extension of the crust, which deviates from the regional compressive stress. The deviation is possibly caused by the Nordic landmass' rebound following deglaciation, and rapid sediment redistribution. The fractures and fluids in the upper crust, in conjunction with the Moho step, can further change the stress condition and promote earthquakes in the region.