M6.1 aftershock hits near the coast of Alaska Peninsula, U.S.


A strong aftershock registered by the USGS as M6.1 hit near the coast of Alaska Peninsula, U.S. at 08:03 UTC on July 28, 2020, at a depth of 41.3 km (25.6 miles). This is yet another aftershock of powerful M7.8 earthquake that struck at 08:12 UTC on July 22.

USGS registered a total of 104 earthquakes in the region since July 22, including initial M7.8.

There were 2 aftershocks with magnitude 6.1, 7 with magnitudes between 5 and 5.8, and 25 with magnitudes between 4 and 5.

Earthquakes registered by the USGS in 7 days to July 28, 2020. Image credit: TW/SAM, Google

Today's earthquake was located 66.3 km (41.2 miles) SW of Sand Point and 963 km (598 miles) SW of Anchorage.

There are about 2 000 people living within 100 km (62 miles).

There is no tsunami threat from this earthquake.

2 000 people are estimated to have felt light shaking.

The USGS issued a green alert for shaking-related fatalities and economic losses. There is a low likelihood of casualties and damage.

Overall, the population in this region resides in structures that are resistant to earthquake shaking, though vulnerable structures exist. The predominant vulnerable building types are unreinforced brick masonry and reinforced masonry construction.

Image credit: TW/SAM, Google

More earthquakes can be expected in the region over the next 7 days.

According to the USGS aftershock forecast, the chance of an earthquake of magnitude 3 or higher is > 99%, and it is most likely that as few as 16 or as many as 64 such earthquakes may occur in the case that the sequence is re-invigorated by a larger aftershock.

The chance of an earthquake of magnitude 5 or higher is 29%, and it is most likely that as few as 0 or as many as 3 such earthquakes may occur.

The chance of an earthquake of magnitude 6 or higher is 3%; the chance of magnitude 7 or higher is 1 in 300, such an earthquake is possible but with a low probability.

Regional seismicity

Featured image credit: TW/SAM, Google


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