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Originally posted by westcoast
The earthquakes tend to break a little deeper, and are coupled better to the ground, so also have more high frequencies than the current events.
The Cascades Volcano Observatory and the PNSN cooperatively operate 11 seismometers on or near Mount Rainier. On average, we locate 0 to 2 earthquakes within 10 km of the volcano each week. Mount Rainier and the nearby Western Rainier Seismic Zone occasionally produce swarms of many small earthquakes. An additional challenge on Mount Rainier is that its glaciers also produce small swarms of icequakes.
Cryoseisms are often mistaken for minor or intraplate earthquakes. Although the outward signs often appear similar to those of an earthquake, with tremors, vibrations, ground cracking and related noises such as thundering or booming sounds, cryoseisms can be distinguished from earthquakes through meteorological and geological conditions. Cryoseisms can have an intensity of up to VI on the Modified Mercalli Scale. Furthermore, cryoseisms often exhibit high intensity in a very localized area, in the immediate proximity of the epicenter, as compared to the widespread effects of an earthquake. Due to lower frequency vibrations than earthquakes, some seismic monitoring stations may not record their occurrence. Although cryoseisms release less energy than most tectonic events, they can still cause damage or significant effects at the site.
Thousands of 'ice quakes' detected on Mount Rainier
by GLENN FARLEY / KING 5 News
Posted on June 9, 2010 at 4:51 PM
Updated Wednesday, Jun 9 at 8:43 PM
SEATTLE - You can see them on the seismometers at the Pacific Northwest Seismic Network at the University of Washington. There are thousands of them - little squiggles that come every few minutes. Scientists call them "ice quakes" along with a few other names.
"We think it's glacial noise coming from the bottom of a glacier." said Dr. Steve Malone, a UW professor emeritus and expert on the seismicity of volcanoes. Among other things, he tracked the buildup to the explosive eruption of Mount St. Helens in 1980.
But Malone does not think Mount Rainier is coming back to life because of where the quakes are, high on the mountain and on the surface of the rock, not deep down inside where signs of moving magma would be detected.
Some reports have indicated the presence of "distant flashing lights" before or during a cryoseism, possibly due to the electrical changes when the rocks are compressed. Cracks and fissures can also appear, as the ground may contract and split apart from the cold. These, usually superficial, cracks range from several centimetres to several kilometres long, with either a single linear fracture or multiple ones as well as small vertical and moderate lateral displacement.
The signature on the seismometer is also different. Where volcanic earthquakes start with a sudden bang and then peter out, these start with a whimper, get bigger and then trail off.
There's another one every few minutes, but they are small, less than a magnitude 1. In other words, they can't be felt.
They are also showing up on just three seismometers higher up on the mountain, one of them located near a popular stopping point for climbers known as Camp Muir.
They have been seen before. There were similar swarms in 1990 and 1998, but not this long. This latest wave began on May 21, faded away as June began and has picked up to a steady clip ever since.
"It's interesting. It's one of these scientific curiosities," said Malone.
send their waves out through the lossy shallowest few hundred meters of the volcano, which damps out the high frequencies
Where volcanic earthquakes start with a sudden bang and then peter out, these start with a whimper, get bigger and then trail off
They include not only tectonic earthquakes, but also ice related phenomena possibly involving recent global climate change.
Summary Several kinds of natural signals were recorded by a seismic experiment on the continental ice sheet in Eastern Dronning Maud Land during the 2002 austral summer. They include not only tectonic earthquakes, but also ice related phenomena possibly involving recent global climate change. The recorded signals are classified into (1) a teleseismic event, (2) local ice-quakes and (3) an unidentified event (X-phases).
Interestingly, the frequency content at 2.0 Hz is small in the waveforms recorded by stations in middle part of the seismic profile. On the other hand, 5.0 Hz and 1.5 Hz components are large at these stations which are above a valley in topography at the interface between the ice sheet and topmost crust. The abrupt change of topography in the valley might cause both the anomalous frequency content and travel times. The estimated origin of the unidentified event might be an intraplate earthquake or possibly a large ice-quake around East Antarctica.
Citation: Kanao, M., A. Yamada, M. Yama#a and K. Kainuma (2007), Characteristic Seismic Signals Associated with Ice Sheet & Glacier Dymanics, (sic ) Eastern Dronning Maud Land, East Antarctica, in Antarctica: A Keystone in a Changing World – Online Proceedings of the 10th ISAES, edited by A.K. Cooper and C.R. Raymond et al., USGS Open-File Report 2007-1047, Extended Abstract 182, 4 p.
We have described several features of cryoseismic signals, particularly involved in the glacial earthquakes associated with the recent ice sheet dynamics in Greenland.
The last four decades of seismicity in Greenland and surrounding regions were investigated by Kanao et al. (2010), as for the all tectonic and volcanic events plausibly include the glacial earthquakes (Fig. 8). Here, we applied the statistical model of the Epidemic Type Aftershock Sequences (ETAS), on the basis of the Gutenberg–Richter’s magnitude frequency distribution. The ETAS model is a statistical tool for analyzing the occurrence times of earthquakes associated with magnitude, and has been used for the discrimination of seismicity patterns in many regions (Ogata, 1988). The model stochastically classifies earthquakes into aftershocks and background events. The background events are obtained by stochastically removing clustered events or aftershocks. The same procedures were applied for the space-time analyses in seismicity around the Antarctic Plate, particularly in the vicinity of the Balleny Island region (Himeno et al., 2011).
Originally posted by Kaworu
Darn...will have to keep an eye on this thread now. My fiance and I were planing on moving up there within the first quarter of 2012. Seattle to be exact. Don't think this will change are minds but if things get real active then well definitely have to reconsider.
Ranger Shot At Mount Rainier National Park
UPDATED, 1:15 P.M.
A ranger at Mount Rainier National Park was shot this morning near the Longmire Ranger Station. Mount Rainier National Park is closed until further notice, and the Pierce County Sheriff's Department reports that shots are still being fired in the park.