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Magnitude 5.7 - ANTOFAGASTA, CHILE
2011 October 30 18:53:43 UTC
Versión en Español
* Scientific & Technical
* This event has been reviewed by a seismologist.
* Sunday, October 30, 2011 at 18:53:43 UTC
* Sunday, October 30, 2011 at 03:53:43 PM at epicenter
* Time of Earthquake in other Time Zones
Location 25.812°S, 70.567°W
Depth 31.4 km (19.5 miles)
Region ANTOFAGASTA, CHILE
Distances 46 km (28 miles) S of Taltal, Antofagasta, Chile
174 km (108 miles) N of Copiapo, Atacama, Chile
239 km (148 miles) S of Antofagasta, Antofagasta, Chile
847 km (526 miles) N of SANTIAGO, Region Metropolitana, Chile
Location Uncertainty horizontal +/- 20.5 km (12.7 miles); depth +/- 7.7 km (4.8 miles)
Parameters NST=129, Nph=129, Dmin=254.9 km, Rmss=1.12 sec, Gp=137°,
M-type=body wave magnitude (Mb), Version=8
* Magnitude: USGS NEIC (WDCS-D)
Location: USGS NEIC (WDCS-D)
Event ID usb0006glr
Magnitude mb 5.6
Region OFFSHORE ANTOFAGASTA, CHILE
Date time 2011-10-30 18:53:41.0 UTC
Location 25.75 S ; 70.75 W
Depth 10 km
Distances 184 km NW Copiapó (pop 129,280 ; local time 15:53:41.5 2011-10-30)
48 km SW Taltal (pop 10,018 ; local time 15:53:41.5 2011-10-30)
The Earth's magnetic field has reversed many times at an irregular rate throughout its history. Long periods without reversal have been interspersed with eras of frequent reversals. What is the reason for these reversals and their irregularity? Researchers from CNRS and the Institut de Physique du Globe, France, have shed new light on the issue by demonstrating that, over the last 300 million years, reversal frequency has depended on the distribution of tectonic plates on the surface of the globe. This result does not imply that terrestrial plates themselves trigger the switch over of the magnetic field. Instead, it establishes that although the reversal phenomenon takes place, in fine, within the Earth's liquid core, it is nevertheless sensitive to what happens outside the core and more specifically in the Earth's mantle. This work is published on 16 October 2011 in Geophysical Research Letters.
Q: Why do so many earthquakes occur at a depth of 10km?
10 km is a "fixed depth". Sometimes data are too poor to compute a reliable depth for an earthquake. In such a case, the depth is assigned to be 10 km. In many areas around the world, reliable depths tend to average 10 km or close to it. For example, if we made a histogram of the reliable depths in such an area, we'd expect to see a peak around 10 km.
The depth where the earthquake begins to rupture. This depth may be relative to mean sea-level or the average elevation of the seismic stations which provided arrival-time data for the earthquake location. The choice of reference depth is dependent on the method used to locate the earthquake. Sometimes when depth is poorly constrained by available seismic data, the location program will set the depth at a fixed value. For example, 33 km is often used as a default depth for earthquakes determined to be shallow, but whose depth is not satisfactorily determined by the data, whereas default depths of 5 or 10 km are often used in mid-continental areas and on mid-ocean ridges since earthquakes in these areas are usually shallower than 33 km.
Earthquakes at shallow depths are a result of stick-slip faulting, however, below about 50 km the hot, high pressure conditions ought to inhibit further seismicity. The mantle is also considered to be viscous, and so incapable of brittle faulting. However, in subduction zones, earthquakes are observed down to 670 km. A number of mechanisms have been proposed to explain this phenomenon, including dehydration, thermal runaway, and phase change.
The geothermal gradient can be lowered where cool material from the surface sinks downward, increasing the strength of the surrounding mantle, and allowing earthquakes to occur down to a depth of 400 km and 670 km.
Rocks hotter than about 300 degrees Celsius flow in response to stress, they do not rupture in earthquakes
However, due to higher than expected temperatures at this depth and location, 180 °C (356 °F) instead of expected 100 °C (212 °F), drilling deeper was deemed unfeasible and the drilling was stopped in 1992. With the expected further increase in temperature with increasing depth, drilling to 15,000 m (49,000 ft) would have meant working at a projected 300 °C (570 °F), at which the drill bit would no longer work.
Originally posted by radpetey
Someone posted this in another thread around 5:30 pm. in Kentucky.
Keep alert you peeps in NMSZ area.....this is the second or third time since May that these anomalies have been witnessed.
We just observed earthquake lights for about 10-20 minutes to the southwest of our location in Kentucky. The general direction of New Madrid! I've never seen these weird lights before! A relatively small bright spot in the sky with pink to the right and blue-green colors to the left of it. In the middle it was yellowish-white. It came for a few minutes and went away then returned for a few minutes in the same place in the sky.
Also a sulfur smell in our water which has never been there before until a few weeks ago.