Earthquakes

Magnitude 5+ Earthquakes – Global

5.7 Earthquake hits the Alaska Peninsula.

5.1 Earthquake hits southeast of the Loyalty Islands.

5.0 Earthquake hits Taiwan.

5.0 Earthquake hits Halmahera, Indonesia.

Slippery Clay at Fault in 2011 Japan Earthquake

Slippery clay that looks like scaly black dragon skin is the crucial clue needed to explain the 2011 Japan earthquake’s surprising impact, according to three studies published Dec. 5 in the journal Science.

The clay, which resists slipping just slightly better than a banana peel, lines the shallow part of the massive plate boundary fault offshore of Japan, where the seafloor jumped eastward by a staggering 165 feet (50 meters) on March 11, 2011. The enormous surge gave the ocean a giant slap, generating the destructive tsunami that killed more than 15,000 people.

The Tohoku quake was a magnitude 9.0, but it was like no subduction quake ever seen before. Before the 2011 earthquake, scientists thought subduction zones concentrated their energy deeply, where rocks are strong and plates can stick together between quakes. (Faults store energy between earthquakes kind of like springs, slowly squeezing until the boundary unleashes and everything rips apart.) But the Tohoku temblor was a surprise — the shallow part of the fault shifted twice as much as the deeper part. These soft, muddy rocks were expected to be too weak to store energy between earthquakes.

“We’d never seen such large slip happen at very shallow depth in a subduction zone before.”

The studies conclude the dragon-skin clay was the earthquake’s weak link. The slippery clay helped the plates slide so far during the 2011 temblor.

And because the clay layer is a distinctive marker found buried across the Northwest Pacific seafloor, scientists fear subduction zones near Alaska and Russia may also hide this clay. If so, their potential for powerful tsunamis could be greater than thought.

Storms and Floods

Hurricane “Xaver”

Xaver brought a fierce and stormy night to many parts of Germany. The North Sea continued to batter against dikes in the early hours of Friday, with storm winds snapping trees and damaging buildings in the country’s north.

In the port city of Hamburg, the flood reached a level of 6.09 meters above sea level by 6:30 a.m., however, despite danger warnings being issued ahead of the surge, the water level has already begun to recede. The storm has caused only a few accidents involving injuries in Germany.

The German transport ministry said until Sunday people should limit travel by road and rail to journeys which are “absolutely necessary” as train services were also restricted. In preparation for the storm In Hamburg schools and Christmas markets were closed and ferries to Germany’s North Sea islands were kept in port. Warnings were also made in adjoining states of Schleswig-Holstein and Bremen.

After causing huge damage in western Europe, hurricane Xaver hit Poland in the early hours of Friday morning with winds of around 100 km per hour and gusts of 130 km per hour claiming the lives of at least five people in Poland and leaving an estimated 400,000 people without electricity.

NewsBytes

Small tornado hit New Plymouth, New Zealand causing some damage to properties.

Volcanos

Roundup of Global Volcanic Activity:

El Hierro (Canary Islands, Spain): No significant changes have occurred during the past months. Since the last energetic seismic swarm and deformation event in late March / early April this year, earthquake activity has remained more or less stable, although above background (pre-2011) levels. In the past months, averages ranged from 5-10 mostly small (below magnitude 3) daily events. Most of them are clustered at approx. 10 km depth beneath the central part of the island. No significant deformation has taken place in this period either.

Suwanose-jima (Ryukyu Islands): Weak reddish glow can be seen above the active Ontake crater at night. It is possible (if not likely) that there is weak strombolian activity. During the past weeks, a few more energetic explosions produced ash plumes that could be identified by VAAC Tokyo.

Popocatépetl (Central Mexico): Strong degassing with high SO2 content and glow from the crater characterise the current activity. There have been almost no explosive emissions during the past 24 hrs.

Heard (Australia, Southern Indian Ocean): A hot spot at the summit crater is visible on MODIS satellite data, suggesting resumed or ongoing activity of some sort (small lava dome, lava lake?).