Strong EQ Strikes Northern Qinghai, China
Posted by feww on August 28, 2009
Magnitude 6.2 earthquake shakes Northern Qinghai, China, followed by large aftershocks
Strong Earthquake measuring 6.2 Mw struck Northern Qinghai, China, about 35 km ESE of Da Qaidam, Qinghai, China, at a depth of 10 km, on Friday, August 28, 2009 at 01:52 UTC, USGS EHP reported.
The earthquake was followed by at least 4 large aftershocks at the time of writing, two of which measured 5.6 Mw.
Based on FEWW analysis, the earthquake may have been as powerful as a magnitude 6.9 shock, possibly larger, and probably misreported by USGS EHP.
China’s official news agency (Xinhua) reported the event as follows:
6.4-magnitude earthquake jolts NW China
http://news.xinhuanet.com/english/2009-08/28/content_11957440.htm
XINING, Aug. 28 (Xinhua) — An earthquake measuring 6.4 on the Richter scale struck the remote Qinghai Province in northwest China at 9:52 a.m. Friday, the China Earthquake Administration said, but no casualties have been reported.
A total of 128 aftershocks had been registered by 11 a.m. near the epicenter in the Da Qaidam (also known as Dachaidan) district in the Mongolian-Tibetan Autonomous Prefecture of Haixi, with the strongest measuring 5.3 magnitude that struck at 10:14, according to the Qinghai Provincial Seismological Network.
“So far, we have not received reports of casualties or house collapses,” the provincial government said in a statement.
“The governments of the province, the Haixi prefecture and Golmud City have sent staff to investigate,” it said.
The epicenter, at 37.6 degrees north and 95.8 east, was about 140 km away from Delingha City, the capital of the Haixi prefecture, and about 160 km away from Golmud, another major city in Haixi, according to the China Earthquake Administration.
The quake was strongly felt in both cities, the administration said.
The China Earthquake Administration, the National Disaster Reduction Committee and the Ministry of Civil Affairs have all sent staff to the quake-hit region for relief work.
Da Qaidam is a sparsely populated district with an average altitude of 4,000 meters and about 16,000 people, including Mongolians, Tibetans, Muslim Hui and Han. The district covers 34,000 square km and administers three townships.
Da Qaidam, which literally means “a big salt lake” in Mongolian, is rich in mineral resources, with one of the largest lead-zinc mines in western China and several coal mines. [Emphasis added by Moderator.]
On Nov. 10 last year, a 6.3-magnitude quake struck Da Qaidam but did not cause casualties. The quake only toppled several huts and caused cracks in the walls of some mud houses.
In April 2003, a 6.6-magnitude quake hit the same region but did not cause casualties, either, and only damaged old buildings. Editor: Anne Tang – copyright the news agency.
FEWW strongly believes that this earthquake was triggered by human activity, especially the extensive mining operations in the region.
10-degree Map Centered at 40°N,95°E
Earthquake Location Map. Original map: USGS EHP. Image upgraded by FEWW.
- Magnitude: 6.2
- Date-Time: Friday, August 28, 2009 at 01:52:06 UTC
- Location: 37.721°N, 95.684°E
- Depth: 10 km (6.2 miles)
- Region: NORTHERN QINGHAI, CHINA
- Distances:
- 35 km (20 miles) ESE of Da Qaidam, Qinghai, China
- 165 km (100 miles) NNE of Golmud, Qinghai, China
- 1815 km (1120 miles) W of BEIJING, Beijing, China
- Location Uncertainty: horizontal +/- 8.1 km (5.0 miles); depth fixed by location program
- Parameters: NST= 79, Nph= 79, Dmin=>999 km, Rmss=0.92 sec, Gp= 94°, M-type=teleseismic moment magnitude (Mw), Version=7
- Source: USGS NEIC (WDCS-D)
- Event ID: us2009kwaf
Historic Seismicity (Magnitude 7+ since 1900)
Major Tectonic Boundaries: Subduction Zones -purple, Ridges -red and Transform Faults -green
In November 2008, a mainshock measuring 6.3 Mw struck Da Qaidam area, followed by a swarm of aftershocks with the three largest shocks measuring 5.4, 5.2 and 5Mw.
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feww said
10th strong aftershock shakes Northern Qinghai, China
Magnitude 5.8
Date-Time: Monday, August 31, 2009 at 10:15:30 UTC [Monday, August 31, 2009 at 06:15:30 PM at epicenter]
Location: 37.697°N, 95.899°E
Depth: 10 km (6.2 miles)
Region: NORTHERN QINGHAI, CHINA
Distances:
+55 km (35 miles) ESE of Da Qaidam, Qinghai, China
+170 km (105 miles) NNE of Golmud, Qinghai, China
+1800 km (1110 miles) W of BEIJING, Beijing, China
Location Uncertainty: horizontal +/- 5.4 km (3.4 miles);
Parameters NST= 99, Nph= 99, Dmin=>999 km, Rmss=0.93 sec, Gp= 40°, M-type=teleseismic moment magnitude (Mw), Version=7
Source: USGS NEIC (WDCS-D)
Event ID: us2009kzaw
Note: Unless a great seismic event [magnitude of about 7.8 to 8.2] is about to occur close to this ‘aftershock,’ the reported details of this event seem to be inconsistent with the magnitude of Friday’s mainshock [6.2 Mw.]
See also FEWW comments in the main post.
see also FEWW comment in the main enrty:
feww said
USGS Earthquake Hazards Program has for a 2nd time downgraded the aftershock to a magnitude 5.6, presumably in an effort to make sense of their initial “error.”