Monday, May 12, 2008

Richter 7.9 Earth Quake hit right at Wolong Panda Reserve



The longitude and latitude data shows that the epicenter is a few km from the Wolong Panda Reserve.

Update: USGS revised the magnitude to 7.9 now (was 7.8, initially at 7.5). There are now OVER 20 aftershocks, all around 4.9-6.0 grade in Richter.

  • MAG UTC DATE-TIME y/m/d h:m:s deg LON deg DEPTH km Region
  • MAP 5.0 2008/05/13 03:00:38 31.222 103.671 10.0 EASTERN SICHUAN
  • MAP 5.3 2008/05/12 23:54:47 31.307 103.576 10.0 EASTERN SICHUAN
  • MAP 5.4 2008/05/12 23:46:19 31.319 103.501 10.0 EASTERN SICHUAN
  • MAP 4.6 2008/05/12 21:08:14 31.385 103.436 10.0 EASTERN SICHUAN
  • MAP 4.8 2008/05/12 20:51:26 32.312 104.958 10.0 SICHUAN-GANSU
  • MAP 5.3 2008/05/12 20:45:31 31.759 104.420 10.0 EASTERN SICHUAN
  • MAP 5.6 2008/05/12 20:08:48 31.420 103.906 10.0 EASTERN SICHUAN
  • MAP 4.4 2008/05/12 18:55:21 32.223 104.850 10.0 SICHUAN-GANSU BORDER
  • MAP 5.1 2008/05/12 17:54:32 31.250 103.492 10.0 EASTERN SICHUAN
  • MAP 4.8 2008/05/12 17:52:23 31.891 104.449 10.0 EASTERN SICHUAN
  • MAP 4.9 2008/05/12 17:03:10 31.133 103.586 10.0 EASTERN SICHUAN, CHINA
  • MAP 5.1 2008/05/12 15:28:54 31.129 103.391 10.0 EASTERN SICHUAN
  • MAP 5.1 2008/05/12 15:05:31 31.258 103.700 10.0 EASTERN SICHUAN
  • MAP 5.1 2008/05/12 14:46:08 32.709 105.617 10.0 SICHUAN-GANSU BORDER
  • MAP 5.1 2008/05/12 14:15:26 32.120 104.612 10.0 SICHUAN-GANSU BORDER
  • MAP 4.9 2008/05/12 13:40:55 31.023 103.526 10.0 EASTERN SICHUAN
  • MAP 4.9 2008/05/12 12:15:42 31.898 104.623 10.0 EASTERN SICHUAN
  • MAP 5.8 2008/05/12 11:11:02 31.249 103.693 10.0 EASTERN SICHUAN
  • MAP 5.1 2008/05/12 10:23:40 30.992 103.413 10.0 EASTERN SICHUAN
  • MAP 5.5 2008/05/12 09:42:25 31.519 104.116 10.0 EASTERN SICHUAN
  • MAP 4.9 2008/05/12 09:23:35 32.142 104.894 10.0 SICHUAN-GANSU BORDER
  • MAP 5.1 2008/05/12 09:07:01 31.255 103.788 10.0 EASTERN SICHUAN
  • MAP 5.0 2008/05/12 08:47:25 32.215 105.029 10.0 SICHUAN-GANSU BORDER
  • MAP 4.9 2008/05/12 08:26:13 31.399 103.957 10.0 EASTERN SICHUAN
  • MAP 5.2 2008/05/12 08:21:41 31.542 104.085 10.0 EASTERN SICHUAN
  • MAP 5.2 2008/05/12 08:10:59 31.225 103.574 10.0 EASTERN SICHUAN
  • MAP 5.4 2008/05/12 07:34:43 31.278 103.799 10.0 EASTERN SICHUAN
  • MAP 5.7 2008/05/12 06:54:18 31.155 103.826 10.0 EASTERN SICHUAN
  • MAP 6.0 2008/05/12 06:43:15 31.225 103.761 10.0 EASTERN SICHUAN
  • MAP 7.8 2008/05/12 06:28:01 31.104 103.270 10.0 EASTERN SICHUAN


Note the aftershocks form a line, which is likely the "fault line" or "earthquake belt". For more updated map see here.

The lines joins the locations of different aftershocks. Red lines are the first 6 after-quakes. Blue line is the more recent after-quakes (colored differently for easy reading)


zoomed in, Chengdu in SW corner (you can see the longitude/latitude in lower left corner)


Earthquake wave sent from 1500km was felt here in Beijing, especially by those in high rises


  • Richter scale 7.8
  • Epicenter is 10km below ground level, which explains why the wave was able to reach as far as Beijing and Shanghai (Quakes closer to surface tend to be localized and absorbed in its neighborhood)
  • The epicenter is just north of the famous Dujiangyan, in Wenchuan County, which is part of Aba Tibetan and Qiang Autonomous State. From the map above we see the epicenter (and those of aftershocks) are all in the mountains, which is supposedly sparsely populated (in Chinese standard)
  • Note the epicenter is very close to the Famous Panda Reserve (Wolong)
There is no need to panic. Unless you live in the area west of Chengdu, Sichuan. But even in Sichuan, as we know, the after-quakes are in general mild comparatively. Note also that the apparent quake is much stronger upstairs, for the same degree of displacement (elementary geometry. It was said the you add 1 grade for every 6-8 floors up.

The epicenter is west of Mianyang, in Wenchuan County, the mountain NW of Chengdu Basin, where the slopes begin to climb to the east part of Qinghai-Tibet Plateau.

For those who are still worried, let me tell you there had been over 10 of after-quakes over grade 5, which you did not feel (so it is unlikely that you will feel more quake at your localities)


With so many after-quakes, whatever unstable structures that is still there 10km underground should have more or less settled into something more stable.

It has also been noted that the high-rises in Beijing and Shanghai shook for 1-2 minutes. This is a result of "dispersion", i.e. when a wave transmitted through a distance, it spreads. (Technical note: because any wave is a superposition of different harmonics (difference frequencies in a fourier series), and the speed for difference frequencies are different, so the further it travels the wider the wave is spread apart)

Rumours, as usual, are passed by the unscrupulous. Such as this one

  • "中国地震局刚刚发布公告：北京时间08年05月12日14点30分左右北京局部地区发生2级轻微地震另警告在08年05月12日晚上22点至24点时间段北京局部地区还会有2-6级地震 望大家提前做好预防措施 --中国地震局 08年05月12日告"
It is easy to spot the flaws in these rumours. e.g.

  • if you go to geology website, it would be quick to know that there is no such grade 2 earthquakes (USGS site list all earthquakes above 2.5 over the world)
  • No earthquake prediction will say things as precise as 2200-2400pm or grade 2-4One simple way to verify is to check the website of the source, i.e., the so called "中国地震局"
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