Petryl Hsieh
LARGEST QUAKES -
This morning -
None 5.0 or higher.
Yesterday -
9/20/11 -
5.1 VANUATU
5.0 NEAR EAST COAST OF HONSHU, JAPAN
5.1 SOUTHERN MID-ATLANTIC RIDGE
5.5 CENTRAL EAST PACIFIC RISE
VOLCANOES -
Volcano oozes lava on Alaskan Aleutian Island - The Mount Cleveland volcano is erupting with the effusion of lava within the summit crater on an uninhabited island about 1500km (940 miles) south-west of Anchorage. Satellite data last week showed a "thermal anomaly," indicating the lava dome was growing.
Observers were able to measure the lava dome at 165 metre in diameter, up from 150 metres on September 9. The lava dome remains about 20 metres below the eastern rim of the summit crater. The observatory says a growing lava dome increases the possibility of an explosive eruption that could send ash high into the sky.
Lava overflowing the rim is another possibility.
INDIA - Quake toll mounts to 92. More than 3000 people were rescued in quake-hit areas of Sikkim by defence forces which scrambled hard to clear debris of collapsed structures and landslides as the death toll in Sunday's powerful temblor shot up to 92. Rescuers on Wednesday struggled to reach the devastated areas where "heavy casualties" were feared.
Sikkim quake UNUSUAL, say geologists - The earthquake that rocked Sikkim Sunday is unusual in terms of its "unusually greater magnitude" and nature of origin. It is different from the usual Himalayan thrust earthquakes that are caused by the collision of the Indian plate with the Eurasian plate. These earthquakes are different in the sense that they are along the somewhat north-south structures trending transverse to the east-west Himalayan axis. "This 6.9 magnitude earthquake possibly occurred on a northwest-southeast trending almost vertical fault through strike slip motion. This is what we generally do not expect in the Himalayas. We expect large magnitude earthquakes on the detachment having thrust motion on gently dipping planes - like the 1999 Chamoli and 1991 Uttarkashi earthquakes...This is POSSIBLY THE LARGEST MAGNITUDE EARTHQUAKE OF THIS TYPE IN THE HIMALAYAS."
Geologists are also surprised at the fewer number of aftershocks - only two to three aftershocks of magnitude greater than 4.5. "So where are all the aftershocks gone? Are they yet to occur in the following days? We need to be careful" if, in the coming days, the aftershocks occur southeast of the main shock epicentre - the way two aftershocks have occurred. "The region where the main shock occurred has very low population density, but further southeast, population density is higher. The occurrence of this earthquake does not lower down the threat from the great earthquake which we expect in the Himalayas." The one (or more) which is expected will be a thrust type earthquake on the detachment which will be much more devastating than this one. "We need to treat each and every earthquake in a special way, you just need to turn it around and it will tell a somewhat different story." Geologists do not think this particular event in Sikkim can be treated as a precursory signal to any major earthquake that may occur in future along the Himalayan arc. "Having said that, the fact remains that some historically earthquake-deficient parts of the Himalayas has the potential to generate large earthquakes any time, irrespective of the present earthquake."
TROPICAL STORMS -
In the Atlantic -
Tropical storm Ophelia was located about 1585 mi (2555 km) ESE of the northern Leeward Islands. There are no coastal watches or warnings in effect.
In the Pacific -
Typhoon Roke was located approximately 230 nm southwest of Yokosuka, Japan. Roke should make landfall in the southwest of Tokyo, near Hamamatsu (Shizuoka Prefecture) today.
Japan braces for strong typhoon - More than a million Japanese have been warned to leave their homes, as a strong typhoon is forecast to land and make its way across Japan's largest island of Honshu today. The Japan Meteorological Agency was calling for "the greatest possible vigilance" as Typhoon Roke, bringing strong winds and heavy rain, approached this morning. As of 10am local time (11am AEST), the typhoon was located some 40 kilometres off the southern-most tip of the Kii Peninsula.
The storm was heading northeast toward the Tokai region in central Japan at a speed of 35 kilometres per hour, packing winds of up to 216km/h. It will likely reach Fukushima prefecture, which was severely hit by the March 11 earthquake, tsunami and ensuing nuclear disaster, about 9pm local time. The city of Nagoya, a regional commercial hub located near the home of Toyota Motor, issued an evacuation advisory to some 1.09 million residents at one point yesterday because of worries that rivers might burst their banks. The advisory was lifted from parts of the city, but landslide, flooding and tornado warnings affected more than a million people were still in place as night fell.
UPDATE - Powerful typhoon Roke has made landfall in Japan, killing four people and lashing some areas with heavy rainfall.
