update apr 27 4.3 quake: http://earthquake.usgs.gov/earthquakes/recenteqsus/Quakes/nn00335238.html
update april 21 800 pdt the swarm seems to be waning this morning both in intensity and frequency, with 11 quakes total on the 20th and only 3 so far this morning. We’ll see how it goes the next couple of days. There was a cluster of quakes down on the border last night near Mexicali, over four hundred miles south of Hawthorne.
update apr 19 “To better monitor the evolving swarm, members from the Nevada Seismological Laboratory, working with the Nevada Division of Emergency Management, have deployed additional seismometers around this sequence to upgrade earthquake locations and, in particular, the depth of earthquake initiation.
“A shallower depth would have the potential for greater damage to buildingsin the area,” Kent said. “The more information we have about this swarm, and more accurately know the magnitude and the depth, the better emergency services can prepare and respond. Given the occurrence of volcanic activity in the region during the past 10,000 years, seismologists will also be looking for signs of tremor in case there is a magmatic origin to this sequence. Evidence thus far points to a tectonic origin, but all scenarios must be investigated.””
update april 18 mon: 3.0 quake mammoth lakes (50 miles s of hawthorne and near the long valley caldera.) http://earthquake.usgs.gov/earthquakes/recenteqsus/Quakes/nc71560731.html
background: “Known quake activity in this area goes back as far as 1974. Since 1974, the CISN (California Integrated Seismic Network) has located more than 3,200 quakes within the box defined by latitude 37.85º – 38.15º, longitude -119.25º – -118.5º. During the past 20 years 170 quakes had magnitudes that exceeded 3.0. The largest quake in the area was a 6.3M that occurred in 1934 south of the Hawthorn swarm.”
more @ link
update apr 17 It seems for the last week 24/7 the area has experience a quake every 40 min or so 24/7. Most of the substantial 3+ mag quakes are at a depth of 12 to 15 miles, with many of the lighter quakes at shallower depths. On the first day April 10 of this current swarm there were 4 substantial quakes in the 9 to 10 mile depth and one at 6 miles. So the trend appears to be currently deeper than at the onset. Also there have been swarms at this location in the past, I think as recently as January this year and maybe in 2004 as well. I will look for some solid links on previous swarms @ Hawthorne.
update: Here is some background. To the north of these quakes you will see Walker Lake. Walker Lake is named after the Walker Lane, a geologic trough feature that runs from southern Oregon through Nevada and ends in southern California near Death Valley. from wikipedia:
The Walker Lane is a geologic trough roughly aligned with the California/Nevada border southward to where Death Valley intersects the Garlock Fault, a major left-lateral strike-slip fault. The north-northwest end of the Walker Lane is between Pyramid Lake in Nevada and California’s Mount Lassen where the Honey Lake Fault meets the transverse tectonic zone forming the southern boundary of the Modoc Plateau and Columbia Plateau provinces. The Walker Lane takes up 15 to 25 percent of the boundary motion between the Pacific Plate and the North American Plate, the other 75 percent being taken up by the San Andreas Fault system to the west. The Walker Lane may represent an incipient major transform fault zone which could replace the San Andreas as the plate boundary in the future.
The Walker Lane deformation belt accommodates nearly 12 mm/yr of dextral shear between the Sierra Nevada-Great Valley Block and North America. The belt is characterized by the northwest-striking trans-current faults and co-evolutionary dip-slip faults formed as result of a spatially segregated displacement field.
update april 16 1800 PDT mag 4.6 one of the largest yet.
|Depth||0 km (~0 mile) set by location program|
|Location Uncertainty||Error estimate not available|
|Parameters||NST= 57, Nph= 57, Dmin=55.3 km, Rmss=0 sec, Gp=108°,
M-type=local magnitude (ML), Version=7
site of todays (4.6 4-16) looks like an open pit strip mine to me:
update – swarm continues for 5th day, Univ. of Nevada sending in more monitoring equipment:
update: ““the (U.S.) Army is drilling two geothermal wells at its Hawthorne Army Depot to power a generating plant that will be capable of providing electricity to approximately 50,000 homes in Western and Northern Nevada as well as the base, according to a senior Pentagon official.”
The earthquake swarm that began on April 10 and then subsided for a day has restarted on the 13th.
4 earthquakes of 3 and 4 magnitude in less than an hour.
3.1 2011/04/13 15:59:19 38.379N 118.738W 16.6 19 km (12 mi) SSW of Hawthorne, NV
1.4 2011/04/13 15:37:55 38.385N 118.745W 18.2 19 km (12 mi) SW of Hawthorne, NV
4.2 2011/04/13 15:16:08 38.386N 118.742W 15.4 19 km (12 mi) SW of Hawthorne, NV
3.6 2011/04/13 15:15:20 38.379N 118.752W 12.0 20 km (12 mi) SW of Hawthorne, NV
4.4 2011/04/13 15:10:08 38.371N 118.748W 13.1 20 km (13 mi) SSW of Hawthorne, NV