人口（ 2004 ） 87,250,000...

人口（ 2004 ） 87,250,000

四川位於長江上游，是中國內陸腹地省份之一，全省東西長 1075公里，南北寬921公里，面積 48.41萬平方公里。四川西部地區是青藏高原的一部分，東部地區則大都位於四川盆地內。四川與重慶、陝西、甘肅、青海、雲南、貴州和西藏自治區接壤。以龍門山 -大涼山一線為界，四川大致可分為東部四川盆地及盆緣山地區，以及西部川西高山高原及川西南山地區。四川地形複雜多樣，包含四川盆地、青藏高原、橫斷山脈、雲貴高原、秦嶺 -大巴山山地等幾大地貌單元，地跨中國地勢第一及第二階梯，西高東低，由西北向東南傾斜。全省最高點是川西的大雪山主峰貢嘎山，海拔 7556米。

四川 (Sichuan)

四川省，簡稱川或蜀，是中國西南地區的一個省，省會位於成都。四川自古被譽為「天府之國」。北宋將原位於四川一帶的川峽路一分為四，設立益州路、梓州路、利州路和夔州路，合稱為「川峽四路」，簡稱「四川路」，四川由此得名。

Page created by W. G. Huang

Earthquake InformationEuropean-Mediterranean Seismological Centre

Credit EMSC

Summary:

Magnitude Mw 7.9

Region EASTERN SICHUAN, CHINA

Date time 2008-05-12 at 06:27:59.0 UTC

Location 31.12 N ; 103.24 E

Depth 10 km

Distances 94 km NW Chengdu (pop 3,950,437 ; local time 14:27 2008-05-12)39 km W Guangkou (pop 65,379 ; local time 14:27 2008-05-12)

200805120627Mw=7.9, D=10 km


Himalayan Mountain Range

Sich

uan

The rugged The rugged SichuanSichuan

Tibetan Plateau

Tarim

Page created by W. G. HuangCredit DigitalGlobe

Credit NASA

Himalayan Mountain Range

Tibetan Plateau

The Himalayan Mountain Range runs a curving path from west to east in this true-color image. In this image, the Range separates southeastern China from India, and runs through (from left to right) northwestern India, Nepal, a small bit of northeastern India, and Bhutan.


Burma

Vietnam

India

Laos

Sich

uan

Tibetan Plateau

EpicenterEpicenter

Credit INGV

Epicenter


This elevation map shows the region where the earthquake struck. Elevations—green indicating the lowest, and beige indicating the highest—are based on data collected by NASA’s Shuttle Radar Topography Mission (SRTM) flown in 2000.

Earthquake Near Chengdu, China (as of May 2008)

Page created by W. G. HuangPage created by W. G. Huang

Regional seismicity before the main shock

From 12/05/2006 to 12/05/20082 events with magnitude <=5.2

Credit EMSC Page created by W. G. Huang

The aftershocks are distributed along an approx. 300 km long North-East direction which is consistent with the mechanisms reported by Harvard and the USGS as well as with the regional topography. As the main shock epicentre is located at the South-West end of the aftershock distribution, the main shock rupture propagated towards the North-East.

Credit EMSC

MOMENT TENSORSSOLUTIONS

Aftershocks distribution (From main shock to 15/05/2008)72 events with magnitude M>=4.5; None with M>6

Page created by W. G. HuangCredit EMSC

Aftershock Animation

都江堰成都

汶川

九寨溝

重慶

綿陽

昆明

蘭州

Credit GFZ Potsdam Page created by W. G. Huang

Affected Areas ( 受地震影響的範圍 )

2008 Sichuan earthquake


China: Mapping the earthquake zone

都江堰

成都

映秀綿竹

北川汶川

綿陽

德陽什邡

Page created by W. G. HuangCredit BBC

川西鎖鑰

195 km


臥龍保護區 Page created by W. G. Huang

80% of houses destroyed

Middle school collapsedAnd over 50 studentsReported dead900 student buried

EpicentreMw=7.9Time 2:28 (local time)

Beichuan

8000 feared dead20,000 injured

Wenchuan

Communication facilities, roads, houses damagedAreas unreachableLandslides reported

China: Earthquake (as of 12 May 2008) - Situation Map

Page created by W. G. HuangcCredit ReliefWeb

80% of houses destroyed

Middle school collapsedAnd over 50 studentsReported dead900 student buried

959 deadRescue teams tricking into worst hit area north of Chengduc

15,000 dead64,746 injured25,000 buried14,000 missing

Communication facilities, roads, houses damaged Troops reached epicentre by parachute

Mianyang (7,395 dead)

Beichuan

Wenchuan

Chengdu

China: Earthquake (as of 14 May 2008) - Situation Map

Page created by W. G. HuangcCredit ReliefWeb

21,500 dead150,000 injured14,000 buried13,400 pulled out alive from debris571,400 houses collapsed279,900 houses destroyed5.7 million people evaccuated

189 deads

Communication facilities, roads, houses damaged Troops reached epicentre by parachute

Wenchuan

959 deadRescue teams tricking into worst hit area north of Chengduc

Chengdu

China: Earthquake

(as of 16 May 2008) - Situation Map

Page created by W. G. Huangc

Credit ReliefWeb

67,183 dead361,822 injured20,790 missing45.61 million affected5.9 million homes damaged5.46 million homes destroyed15 million relocatedCredit ReliefWeb Page created by W. G. Huangc

Credit ReliefWeb

Page created by W. G. HuangCredit ReliefWeb

都江堰

Detected radar anomalies(possible damages tobuildings infrastructures)

Buildings and roads destoryedBuildings and roads destoryed

Buildings destoryedBuildings destoryedFlooded areaFlooded area

Road damaged by landslideRoad damaged by landslide

LandslideLandslide


Buildings destoryedBuildings destoryed

Buildings destoryedBuildings destoryed

Flooded areaFlooded area

Road damaged by landslideRoad damaged by landslide

LandslideLandslide


Page created by W. G. HuangCredit GFZ

Tectonics of the May 12 Sichuan earthquake

中評社香港 5月 17日電／台灣“中央大學”地球科學系教授王乾盈說，四川強震成因被認為“漸歸沉寂”的龍門山斷層“復活”發生錯動，這個斷層自明朝以來錄得震動的數據不多；本月 12日的錯動使當地地殼抬升九公尺，“喜馬拉雅山也隨之長高好幾公尺”。

王乾盈說，四川過去百年來發生的大小地震，只有少數跟龍門山斷層有關，規模不大，“以前長時間地震釋放的能量，幾乎都被同在四川的鮮水河斷層消耗掉”，地震專家都以為龍門山斷層的傷口癒合，不可能再動了。

每秒裂 3 公里裂動一百秒

王乾盈分析，龍門斷層破裂面，從震央汶川縣往北東方向以每秒 3公里速度裂向廣元，足足花一百秒裂完，震災範圍長 240公里、寬 30公里，尤其以破裂至北川縣時錯動得特別厲害。三板塊夾擠地殼抬升 9 米

王乾盈認為，四川地震是因夾在西藏地塊、崑崙地塊、揚子地塊，這三個地塊間的松潘甘孜地塊，向揚子地塊逆衝而上，“年輕的蓋在老的上面”，龍門山斷層要幾千年才會有這麼大的錯動，這次錯動使地殼抬升九公尺，“喜馬拉雅山至少因此長高幾公尺”。


POSTED BY KIM AT 8:27 PMKIM HANNULA

I'm a forty-something tenured geology professor at a small public college in the Rockies. I love mountains - hiking in them, looking at them, studying them. You can reach me at shear sensibility at gmail dot com. My opinions are my own - not my employer's, not my students', not my spouse's, not my graduate advisor's... just mine.

By KIM HANNULA Page created by W. G. Huang

MIT's tectonicist Clark Burchfield is quoted in the NY Times as being surprised that an earthquake of that magnitude (which requires a lot of fault to have moved at once) occurred in this particular spot. But although the size might be larger than one would expect, the type of earthquake isn't. This isn't a classic plate boundary earthquake, but it's part of the way that continents respond to continent-continent collisions.

In the big picture, India is moving northward and colliding with Asia. That's what created the immense mountains of the Himalayas, and the highlands of the Tibetan Plateau, in the first place. This earthquake, however, was not on the plate boundary itself. It was off on the eastern edge of the Himalayas, on the boundary between the high country and the Sichuan basin.

Here's the USGS earthquake location map. The pink lines represent the collisional plate boundaries - the boundary between India and geologic Asia runs along the southern end of the Himalayas. This earthquake was within Asia proper.

Page created by W. G. HuangBy KIM HANNULA

But continents are... well, continents are kind of wimpy, actually, in terms of deformation. They're made of rock that's easier to break than oceanic crust is. And on top of that, they're thick. And when they run into one another, the continental crust gets even thicker. And that thick, weak crust can break within itself - it doesn't behave like the classic rigid plates that "plate tectonics" is named for.

The crust of Asia breaks in a number of different ways. Parts of it are squeezed out, especially to the east, where it can run over the subducting Pacific plate like a semi over a squirrel. Parts of it actually stretch east-west, creating features like Lake Baikal up in Russia. Parts are pushed over each other, making the height of the Himalayas and Tibet possible. And parts are squeezed over other parts of Asia. And that's what's happening on the northwestern side of the Sichuan basin - the edge of the Tibetan Plateau is running over eastern Asia, in this case, along a classic thrust fault, sloping about 30 degrees down into the ground beneath the edge of the mountains.

You can also see the movement of Tibet in this map of GPS velocities:


The map of GPS velocities (From Gan, Zhang, Sun, and Sun, 2006)

Each of the arrows represents the movement of a GPS monitoring site compared to the rest of Eurasia. The southern Himalayas are moving north; the Tien Shan mountains, north of the Tarim basin (white, north of the Himalayas) are moving much more slowly, and the eastern Himalayas... are moving east. Or even south.

And at the Sichuan basin, that green blob east of the Himalayas, the GPS velocities drop. There's a change in movement. And that M 7.9 earthquake took place where the change occurs.


The Google earth image (from the USGS Google earth KML) of the earthquake and its aftershocks shows the setting closer-up:

It looks like the earthquake was on the basin-bounding fault. It looks like there are ridges in the basin running parallel to the fault, too - ridges that are cut by rivers. They are probably actively growing folds... which means there are probably active thrust faults running underneath the basin itself, not just under the mountains. Those faults, at least, don't seem to have moved.


PRESS RELEASE 16th May 2008

Scientists identified earthquake faults in Sichuan, China

Only last summer research published by earth scientists in the international journal Tectonics concluded that geological faults in the Sichuan Basin, China “are sufficiently long to sustain a strong ground-shaking earthquake, making them potentially serious sources of regional seismic hazard."

An international team of scientists including Dr. Alexander Densmore (Durham University), Dr. Mike Ellis (British Geological Survey) and colleagues from research institutes in Chengdu, carefully mapped and analysed a series of geologically young faults that cross Sichuan Province like recently healed scars.

The team mapped the densely populated Sichuan Basin and adjacent mountains using what is known as ‘tectonic geomorphology’. This technique can demonstrate significant changes in ground movement over time, such as observations of offset river channels, disrupted floodplains, abnormally shaped valleys and uplifted landscape features. These subtle signals of deformation, when combined with the ability to measure the age of the disfigured landscapes (using cosmogenic nuclides that bombard the Earth from all corners of the universe), produced surprising results.

Page created by W. G. HuangCredit BGS

The recent earthquake in Sichuan occurred under some of the steepest and most rugged mountains in the world, the Longmen Shan: the Dragon's Gate Mountains. This dramatic range, steeper than the Himalayas, is the upturned rim of the eastern edge of Tibet, a plateau that has risen to 5 km in response to the slow but unstoppable collision of India with Asia that began about 55 million years ago and which continues unabated today.

Two long faults in particular, running almost the entire length of the Longmen Shan, showed clear evidence of slip during the last few thousands, and in some cases hundreds, of years. The rates of slip varied between fractions of mm per year to possibly many mm per year. Millimetre by millimetre, the Longmen Shan are being sliced and displaced much like salami. One of these faults is likely to be the one that gave rise to the 7.9 magnitude earthquake that has now caused 22,069 fatalities. Exactly why the Longmen Shan are here is a mystery. Unlike the Himalaya, which form the southern boundary of Tibet and whose faults chatter continuously with small earthquakes, faults in the Longmen Shan, remnants perhaps of geological events hundreds of millions of years ago, have historically only produced earthquakes up to magnitude 6.

Geomorphological evidence suggests that the mapped faults are very steep with dominantly lateral or strike-slip displacements taking place over time scales of thousands to hundreds of thousands of years. This contrasts with shorter-term measurements using GPS which suggest a greater proportion of thrust or shortening displacement than lateral displacement. The observations of seismologists at the BGS suggest both things: more thrust in the SW, nearer the epicentre, and more strike-slip toward its direction of propagation, the NE.

Page created by W. G. HuangCredit BGS

Map showing seismicity and faulting in the eastern Tibetan plateau region (magnitudes 7.0 and greater labelled).

Credit BGS

1933 7.51976 7.2

1879 8.0

1654 8.0

1718 7.5

Credit BGS

Map showing the distribution of aftershocks following the magnitude 7.9 Mw in Eastern Sichuan on 12 May 2008 (magnitudes 4.5 and greater).

Credit BGS

Credit BGS

Coulomb Failure Stress variation & Vertical displacement

by José A. Álvarez Gómez (Instituto Geografico Nacional, Madrid, Spain) Page created by W. G. Huang

Thanks to the finite fault model provided by the USGS, the author computed the Stress variations and the vertical deformation at the surface promoted by the fault rupture. The equations of Okada (1992), which describe the deformation in a homogeneous elastic half-space due to a rectangular dislocation, and Hooke's law were used to compute the stress tensor. The Coulomb Failure Stress variation (DCFS) was calculated on fault planes equal to the one of the main shock, at a depth of 10 km, that could rupture in the future and is defined as DCFS=T-m'(Sn), where T and Sn are the shear and normal stresses acting on the dislocation respectively, and m' is the assumed apparent friction coefficient of the fault plane (in this case 0.5).

Page created by W. G. Huangby José A. Álvarez Gómez (Instituto Geografico Nacional, Madrid, Spain)

Rupture model of Mw=7.9 08/05/12 Sichuan earthquake


Comparison of the observed waveform (Black) with the calculated waveform (Red). The numbers below the station code indicate maximum amplitude in microns.

Teleseismic stations used in inversion. The star represents the epicenter of the main-shock

Earthquake Research Institute, Univ. of Tokyo The Eastern Sichuan Earthquake(preliminary finite fault model)

（ Analyzed by KazutoHikima, Earthquake Research Institute, Univ. of Tokyo ） Page created by W. G. Huang

Surface projection of the slip distribution

Page created by W. G. Huang（ Analyzed by KazutoHikima, Earthquake Research Institute, Univ. of Tokyo ）

The largest slip occurred at 40 to 60 km north from the hypocenter, and some more asperities (i.e. local maxima of slip) can be also seen. The length and width of the fault are presumed to be 230 km and 40 km, respectively, according to the slip distribution. (For the analyses, we assumed 320 km and 40 km from the aftershock distribution.) The duration time (i.e. time to complete the rupture on the fault) is estimated to be 100 to 120 sec.

Slip distribution on the fault


Adapted from He and Tsukuda, 2003

Longmenshan thrust zone

Kunlun earthquake in 2001


The Longmenshan thrust zone is approximately 60 km wide, and constitutes the topographic boundary between the eastern Tibetan Plateau and the Sichuan basin. The total vertical slip rate is about 1-2 mm/yr, and thus the convergence rate across the thrust zone is inferred to be 4-6 mm/yr.

The northward indentation of the Indian plate into the Tibetan crust after the collision between the Indian and Eurasian plates induced uplift and deformation of the Tibetan Plateau. The continental crust of China, thus, is highly active tectonic area.

This continuing northward indentation resulted in three types of tectonic deformation: convergence zones surrounding the plateau, strike-slip fault zones associated with the laterally extruding crustal blocks in the eastern plateau (i.e. Kunlun earthquake in 2001), and extensional basins in the southern plateau on which the Longmenshan fault is located.


The locations of the downhole arrays and their relationships to the faults around the Taipei metropolitan area. The accelerographic arrays with pink-square are in operation. The broadband arrays are triangulated.


Waveforms Recorded at Taipei Basin Downhole Seismic Network

10 min.

The particle velocities recorded at SNJB at level -100 meters.

Installation of SNJB was completed in November 2007.

E

N

Z


200805120628Mw=7.9

The particle velocities of EW component recorded at DANB at level -90 meters.

200805122008Mw=5.5

200805121111mb=5.7

Sichuan Earthquake’s DevastationMore than 90,000 people are dead, missing or buried under rubble following the devastating earthquake that hit China's Sichuan province last Monday.

Credit BBC Page created by W. G. Huang

May 14, 2006 Images captured by Taiwan’s Formosat-2 satellite

May 19, 2006

the left image shows the region under normal spring-time conditions. Two tiny villages flank the river, the man-made surfaces regularly shaped and bright. The towns are connected by light-colored roads, which line the river on both sides and merge at a bridge where the river narrows on the right.

three days after the initial earthquake, both the bridge and the roads it connected have disappeared under murky water. Some sections of the villages remain above the waterline, as do portions of the roads leading to the villages. The tops of trees, perhaps on slightly higher ground, form tiny islands near the shores of the growing lake.

Yansai Lake in Beichuan County

Formosat-2 took the final image on May 19, 2008. By this time, water levels in the earthquake lake had risen enough to immerse both villages and the entire road network. Tan debris floats on the surface of the water, concentrated over the locations of the villages.

May 15, 2006


before

after

before

after


after

before

In the February 19, 2003, image (bottom) the terrain seems more rugged because the Sun’s low angle cast long shadows at that time of year. Likewise, the brighter red hues in the May 23, 2008, image (top) may result in part from more robust vegetation growing in late spring.

The most dramatic difference between the images, however, is the abundance of bare-ground areas along mountain ridges. Many, if not most, of these areas result from landslides triggered by the May 12 earthquake, and potentially by some of the aftershocks. According to David Petley of Durham University, topographic amplification strengthens an earthquake’s effects on a mountaintop where the shaking is maximized. This leads to landslides that start near the top of a ridge and travel all or most of the way to the valley below.


Thousands are under threat if the water spills over from the 'quake lake‘

About 200,000 people have now been evacuated to higher ground from an area at risk of flooding from a lake formed after the Sichuan earthquake. Residents around the city of Mianyang are being moved as troops dig diversion channels to relieve pressure on the lake, made by landslide-blocked rivers. But there are fears that the dam could burst before they finish.

Yingxiu: epicentre of the earthquake

(ghost of town)


Street view of Yingxiu, July 2005. Rubble on both sides of the street in Yingxiu. Photograph: Jonathan Watts


http://en.wikipedia.org/wiki/Image:Yingxiu_Wenchuan_County_07-28-2005.jpg

http://www.guardian.co.uk/world/gallery/2008/may/20/?picture=334257550

The devastated town of Yingxiu, the rubble is all that is left of the infant schoolPhotograph: Jonathan Watts

Rescuers walk through a section of the elevated expressway brought to earthPhotograph: Jonathan Watts




A motorway tunnel entrance - the road is blocked by a landslide on the other side

Photograph: Jonathan Watts

Troops navigate the speedboats taking people to safety along the Min river

Photograph: Jonathan Watts




A aerial view of the badly stricken town of Yingxiu in Wenchuan County of southwest China's Sichuan Province, two days after a massive earthquake. (May 14, 2008 Xinhua Photo)

Photo taken on May 14, 2008 shows an aerial view of the badly stricken town of Yingxiu in Wenchuan County of southwest China's Sichuan Province, two days after a massive earthquake. (Xinhua Photo)


Photo taken on May 14, 2008 shows an aerial view of the badly stricken town of Yingxiu in Wenchuan County of southwest China's Sichuan Province, two days after a massive earthquake. (Xinhua Photo)

Photo taken on May 14, 2008 shows an aerial view of the badly stricken town of Yingxiu in Wenchuan County of southwest China’s Sichuan Province, two days after a massive earthquake.


These 10 soldiers have just one mission: deliver food and medicines to several towns in Wenchuan county.

An aerial photo taken on May 14 shows the road from Dujiangyan city to Wenchuan County in southwest China's Sichuan Province is destroyed by landslide caused by Monday's earthquake. The serious devastation of the road affected the transportation of rescue teams and relief materials to the disaster areas. (Xinhua Photo)


An aerial view of the remains of the town of Yingxiu

Aerial view of damage of Yingxiu town, Wenchuan


Beichuan: a vision of hellThe day before the earthquake in Beichuan

The last entry on a blog called TGP1963 was posted at 7:49am on May 12. According to Hecaitou the blogger is a science teacher at Beichuan Middle School called Tang Guoping. On May 11, teachers and final year students held a sports fun event. Here are some of the pictures taken that afternoon.


The next day, 80% of the buildings in Beichuan county were destroyed. A thousand children were buried in the middle school.


The devastation is seen in earthquake-affected Beichuan County in Sichuan province

Credit BGS

Earthquake-affected Beichuan County.before

after


Residents look for survivors among the ruins of collapsed apartment blocks in Beichuan

woman cries after she realised a survivor who has just been rescued from a collapsed building is not her husband, in the old city district near a mountain at the earthquake-hit Beichuan county, Sichuan province, May 15, 2008


Residents look for survivors amongst the ruins of collapsed apartment blocks in the city of Beichuan


人口（ 2004 ） 87,250,000...

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