Scientists Identified Earthquake Faults In Sichuan, China in 2007

ScienceDaily (May 16, 2008) — 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 (Institute of Hazard and Risk Research, Durham University), Dr. Mike Ellis (Head of Science for Climate Change at the 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.

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, described in the Tectonics paper, 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 Global Positioning Systems 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.

[ 本帖最後由 snortbsd 於 2008-5-18 13:10 編輯 ]

anyone here can translate into chinese?

that area was identified as earthquake faults in 2007

大概是說四川地區地震形成的原因，主要是從板塊上說。貌似由於板塊移動，龍門山要被拉開了？

抱歉，粗粗瀏覽過，感覺大概是這個意思

原帖由 ancientash 於 2008-5-18 14:14 發表
大概是說四川地區地震形成的原因，主要是從板塊上說。貌似由於板塊移動，龍門山要被拉開了？

抱歉，粗粗瀏覽過，感覺大概是這個意思

no, it says that area was identified as earthquake faults in 2007, which meant before that, that region could be affected by earthquakes, but not likely be an epicenter of earthquake.

definition of fault:

What is a fault? A fault is a break in the earth's crust along which movement can take place causing an earthquake. In Utah, movement along faults is mostly vertical; mountain blocks (for example, the Wasatch Range) move up relative to the downward movement of valley blocks (for example, the Salt Lake Valley).

now we all know tangshan is also a part of an earthquake fault.

[ 本帖最後由 snortbsd 於 2008-5-18 15:08 編輯 ]

謝謝老S提供了這麼好資料，這次又充電了：）

這次地震也要感謝獨運輪的幫助，很多人都學習到了一些地震的知識，或許有些人從此也會立志去研究地質學呢：）

BTW，我查了下金山：FAULT中文解釋是：

【地質學】 斷層：由於地殼的變動或移動而引起的在岩石構成連續性上的破裂，伴之以裂縫的一邊相對於另一邊的錯位也作  shift

『the Longmen Shan are being sliced and displaced much like salami』

我是根據這句話得出來四川龍山將會被撕裂的。

我是根據這句話得出來四川龍山將會被撕裂的

yes. do you know what the word "salami"means? salami is very thin sliced italian sausage, which usually you see them on the top of pizza.

basically no one thought that area could have earthquake with such magnitude and scale until last year, but only at level of science research.

definitely the building code enforcement could be problematic, such as corruptions, but also the building codes themselves would be insufficient for the areas as earthquake epicenters.

please translate this into chinese....

OK,是讓我翻譯你樓上的內容吧？

老S的意思是：

SALAMI是一種義大利臘腸，常見於PIZZA上 -- 就是一片一片的那種。當然，他所轉貼的文章里的意思是指龍山將會如同SALAMI一樣，被切成PIZZA上一片一片的樣子。

第二句的意思是：基本上來說，在07年之前，還沒有人想到這個區域會發生如此高強度的地震（8級左右），僅僅有的一點線索也只是在學術層面。

第三句的意思是：老S認為該地區房屋的抗震等級確實存在著一定的問題，比如由於貪污腐敗等問題造成的豆腐渣工程，但是他同時也認為這些房屋本身既定的抗震係數也無法抵禦來自震中的高強度震波。

如有問題，請老S指出。

原帖由 ancientash 於 2008-5-18 15:52 發表
OK,是讓我翻譯你樓上的內容吧？

老S的意思是：

SALAMI是一種義大利臘腸，常見於PIZZA上 -- 就是一片一片的那種。當然，他所轉貼的文章里的意思是指龍山將會如同SALAMI一樣，被切成PIZZA上一片一片的樣子。 ...

yes!!!!


building code enforcement meant that the law (building codes) enforcement has some problems, too lienant, or just plain corruptions.

http://geology.utah.gov/utahgeo/hazards/eqfault/eqfault.htm

[ 本帖最後由 snortbsd 於 2008-5-18 16:21 編輯 ]

原帖由 snortbsd 於 2008-5-18 16:10 發表



yes!!!!


building code enforcement meant that the law (building codes) enforcement has some problems, too lienant, or just plain corruptions.

http://geology.utah.gov/utahgeo/hazards/ ...

有一個地方不太明白，這個CORRUPTION到底是指人為的貪污腐敗，還是指建築物自然的風蝕腐壞呢？

指人為的貪污腐敗

"zhifar" 確實存在著一定的問題，比如由於貪污腐敗等問題造成的豆腐渣工程, 這些房屋本身既定的抗震係數 too low, 無法抵禦來自震中的高強度震波

但他也解釋說，汶川地震的強度遠遠超出當地所規定的建築抗震標準。

[ 本帖最後由 snortbsd 於 2008-5-18 17:27 編輯 ]