The Solomon Islands Earthquake Cluster
Most of the significant earthquake activity on the planet this week is accounted for by a series of earthquakes just east of the Solomon islands, where a total of 20 tremors of ≥M5.0, (six of them ≥M6.0) occurred. These formed two clusters, one either side of the island of Lata, within the Pacific plate.
The tectonics of the whole of the Pacific-Australian plate margin are complicated. The group of earthquakes occurred at the point where the South Solomon Trench takes a twist before becoming the New Hebrides Trench to the south. Along this boundary the Australian plate is subducting beneath the Pacific plate: rates of convergence are high and so the level of seismic activity in this region reported this week can’t be considered unusual.
Largest Earthquake in the U.S.
An M6.0 near Craig, Alaska, which took place on 2 February seems likely to be an aftershock to the larger (M7.5) Alaskan tremor which struck in early January. That apart, the U.S. again enjoyed a seismically stress-free week. The largest onshore tremor to be felt in the lower 48 states was in Washington State, and registered just M3.7.
When is an Earthquake Not an Earthquake?
The word of the week seems to have been “normal” – but the natural world is full of surprises. What was widely reported as an M4.5 event in southern Austria now appears not to have been an earthquake at all. The Austrian Times newspaper reported that it was the sky, not the Earth, which moved – and that the event was in fact caused by an exploding meteorite.
Austrian Times. Earthquake turns out to be an exploding meteorite. Accessed 5 February 2013.
USGS. M6.9 – 15km SW of Obihiro, Japan. Accessed 5 February 2013.
USGS. Real time earthquake map. Accessed 5 February 2013.
Decoding Science. One article at a time.