Monday, April 8, 2013

Tjörnes Fracture Zone (north of Iceland): ongoing earthquake swarm - The powerful earthquake swarm that started a week ago continues, but at reduced intensity compared to 2 April when the large magnitude 5.4 quake struck. Each day, hundreds of earthquakes have been occurring (more than 200 greater than magnitude 2 on Friday through Saturday).
The earthquake swarm is the result of release of tectonic stress that has accumulated in the crust and is being released at the moment. The area is one of the main so-called transform zones - regions where the separating Eurasian and North-American tectonic plates move sideways along strike-slip faults rather than spreading apart directly as is the case in the main rift zones, where also the main volcanoes are located, because the opening movment here allows large batches of magma to rise easily.
The transform zones separate the rift zones at spreading plate boundaries at regular intervals in order to accommodate differential movements that are a result of the earth's curved surface where rigid plates move apart. In the transform zones, the sideways movement can produce much more strain in the rocks and has therefore the potential of larger earthquakes.
Recent GPS and seismic studies of the TFZ suggest that the plates at depth have been "locked" for a while and accumulated large stress, which is why the recent and present earthquake swarms are no a surprise. It seems that this stress has started to be released right now. However, the possibility of a larger earthquake (up to magnitude 7) remains in place.
The TFZ (as most transform zones) are not particularly prone to volcanic activity, although from time to time, (usually smaller amounts of) magma still can reach the surface in such areas as well. This happens much less so than in the rift zones, where most volcanic activity takes place. For the case of the TFZ, there has probably been an eruption in 1868 following an earthquake swarm, and little else is known about this event. Whether the current activity is related to magmatic activity, or could lead to a submarine eruption in the TFZ is unknown, but unlikely. So far there are no signs that suggest that there is an eruption going on at the sea floor. (maps)

No update on Tuesday this week.

**Knowledge is knowing a tomato is a fruit.
Wisdom is not putting it in a fruit salad.**
Brian Gerald O’Driscoll


Live Seismograms - Worldwide (update every 30 minutes)

This morning -
None 5.0 or higher.

Yesterday -
4/7/13 -
2 in CANARY ISLANDS REGION - largest 3.8

Volcano Webcams

Vesuvius' Next Eruption 'Could Wipe Out Naples' - The next eruption of Vesuvius will threaten three million people, including the entire city of Naples and its suburbs, according to one of the leading scientists monitoring the volcano.


In the South Indian Ocean -
Tropical Cyclone Twenty-one was located approximately 335 nm southwest of Diego Garcia.


Washington - Sounder and Amtrak customers are riding buses again rather than rail lines north of Seattle because of a mudslide that derailed a passenger train Sunday — the latest in what has been an EXCEPTIONALLY BAD SEASON for mudslides.
Sounder service between Seattle and Everett is canceled Monday and Tuesday, when Sound Transit will provide special express buses to and from the Sounder stations. Amtrak expects to resume service Tuesday morning. There were 200 slides during the fall and winter, 50 of them blocking tracks, as of February. The most spectacular hit a moving freight train in mid-December and derailed seven cars. A March 21 slide buried tracks in five feet of debris. Sound Transit has CANCELED A RECORD NUMBER of Northline Sounder runs this rainy season.
None of the train’s 86 passengers and 11 crew members was hurt in Sunday’s slide just north of Howarth Park in Everett, which had little impact on some railcars but badly jostled others. “We almost went over. It was like being tossed around like a rag doll. They hit the brakes immediately. That engineer saved our lives. We would’ve been drug over."
Other passengers saw mud and trees sliding down a cliff and striking the train. “We saw chunks of mud coming down and hitting the train, but it was not as scary as you’d think." The train came to a halt with three cars derailed, two of them visibly tilted off the tracks. The slide, described as 15 feet high and 30 feet wide, prompted the company to issue a 48-hour moratorium on passenger trains on the railway’s double main line. About a quarter mile of track was damaged, but freight trains were able to get through on the adjacent line Sunday and will resume travel on the line where the train was derailed sometime Monday.
Construction is expected to begin later this year on a $16 million, federally funded project to stabilize six or seven spots along the Seattle-Everett corridor that have been prone to mudslides. BNSF will construct retaining walls, remove loose soil and install drainage pipes in soggy areas. A BNSF presentation showed standing water near suburban homes in Mukilteo, and pointed to years of residential development as a contributor to slides. The Washington Department of Transportation warns that much more work needs to be done to fully prevent mudslides.


Another Summer of Drought Looms for Texas and U.S. West - The outlook for the western half of the U.S. continued to be bleak on Thursday, as forecasters said drought conditions are expected to expand and intensify all across the West and Southwest.


Bird flu not spreading between people - There is no proof that the H7N9 bird flu virus is being transmitted between people in China, the World Health Organisation says.