Xiwei Xu Explores the Wenchuan, China Earthquake

Fast Breaking Papers Commentary, February 2011

Xiwei Xu

Article: Coseismic reverse- and oblique-slip surface faulting generated by the 2008 Mw 7.9 Wenchuan earthquake, China


Authors: Xu, XW;Wen, XZ;Yu, GH;Chen, GH;Klinger, Y;Hubbard, J;Shaw, J
Journal: GEOLOGY
Volume: 37, Issue: 6, Page: 515-518, Year: JUN 2009
* China Earthquake Adm, Inst Geol, Beijing 100029, Peoples R China.
* China Earthquake Adm, Inst Geol, Beijing 100029, Peoples R China.
* Earthquake Adm Sichuan Prov, Chengdu 610041, Peoples R China. (Addresses have been truncated)

Xiwei Xu talks with ScienceWatch.com and answers a few questions about this month's Fast Breaking Paper paper in the field of Geosciences.


SW: Why do you think your paper is highly cited?

On May 12, 2008, the Mw 7.9 Wenchuan earthquake struck Wenchuan, Beichuan, and Qingchuan Counties, along the middle segment of the Longmenshan thrust belt, at the eastern margin of the Qinghai-Tibetan plateau and was the most devastating earthquake in China in more than three decades. As of 25th April, 2009, 87,164 deaths have been confirmed, with 374,640 people injured, and many more left homeless.

Major landslides blocked rivers and created unstabilized earthquake-lakes posing additional threat to population in the immediate aftermath of the main event. The maximum meizoseismal intensity (MMI) reached XI around Yingxiu Town, Wenchuan County, and Qushan Town, Beichuan County, where 80% of the houses collapsed during the quake.

Such a devastating earthquake, in fact, not only astonished everyone in the world, but also gave geoscientists a very good chance to understand the seismogenic structure of a great earthquake, earthquake faulting process, features of earthquake disaster distribution, and other scientific problems for earthquake hazard reduction.

"...our research will be applied to reduce future earthquake hazards in China, and attract discussion on the formation of the Qinghai-Tibetan Plateau in academic circles"

Our paper provides a basic data of the earthquake surface rupture features, co-seismic oblique slips and an unusual oblique- and reverse-faulting model, which are very useful for further studies. Moreover, as the paper pointed out, the occurrence of this earthquake demonstrates that at least the upper crust behaves elastically and crustal shortening exists along the eastern margin of the Qinghai-Tibetan Plateau. Thus, owing to above reasons the paper are expected to have the impact it did in the past one and half years.

SW: Why do you think your paper is highly cited? Does it describe a new discovery, methodology, or synthesis of knowledge?

This paper describes a fact that the Wenchuan earthquake generated the longest and most complicated earthquake surface ruptures along the middle segment of the Longmenshan thrust belt at the eastern margin of the Qinghai-Tibetan Plateau in the intra-plate compressive setting.

Based on this fact we also constructed a three-dimensional model for rupture geometry showing that the two sub-parallel surface rupture zones appear to merge at depth and the crustal shortening occurs along the Longmenshan thrust belt at the eastern margin of the Qinghai-Tibetan Plateau. That is, the east-southeastward block motion prevails in the eastern Plateau. Therefore our paper described a new discovery that the crustal shortening does exist along the eastern margin of the Qinghai-Tibetan Plateau.

SW: Why do you think your paper is highly cited?Would you summarize the significance of your paper in layman's terms?

Our results provide the first evidence that multiple faults participated in the rupture and that the slip distribution changed throughout the rupture process. These results have important implications for the general nature of seismic hazards along steep, oblique-thrust fault systems and furnish a better understanding the uplifting mechanism of the Qinghai-Tibetan Plateau.

SW: How did you become involved in this research, and how would you describe the particular challenges, setbacks, and successes that you've encountered along the way?

China has suffered from a lot of destructive earthquakes in history. The government and also the society wish to reduce the earthquake hazards as much as possible. I started working in earthquake geology back in 2001, when I saw a 426-km-long pure strike-slip rupture zone along the western segment of the Kunlun fault during the 2001 AD Mw7.8 Kunlunshan earthquake and was astonished at its long but very narrow surface rupture zone and ~8m left-lateral co-seismic slip. From this earthquake, we learned that the earthquake surface rupture zone is localized by only several decades of meters and can destroy all constructions across it during the quake.

"...the Wenchuan earthquake generated the longest and most complicated earthquake..."

After this observation, I proposed a big project to locate active faults in the urban regions in China by geological surveying, paleo-earthquake trenching, multiple drilling, and strata sample dating. This project has been supported by the central government since 2004 and since then 26 active faults in the 20 mega-cities have been identified and located, which provides a basis for keeping new construction away from the active fault to reduce the possible future earthquake hazards owing to their surface rupturing.

Now this project has been performing in more cities in China. We realize this is a very important project to protect human beings in an earthquake-prone country.

The Wenchuan earthquake, in fact, is quite different in faulting type from the Kunlunshan earthquake. The former is a reverse-slip or oblique-slip faulting earthquake, while the latter is a strike-slip one. Are there different features of their surface ruptures? This is a question mark in my mind after the 2008 Wenchuan earthquake occurrence. Furthermore, the Wenchuan earthquake, which occurred at the eastern margin of the Qinghai-Tibetan Plateau, is a key to test the kinematic model of the Plateau.

Owing to those reasons, we conducted a survey of the surface ruptures within days following the event and the paper presents our surveying result. We wish they are useful for further studies in earthquake mechanism, hazard reduction, uplifting pattern of the Plateau and engineering application.

Having our paper identified as a Fast-Breaking Paper in the field of Geosciences was a nice thing for me to find out. I think every researcher, myself included, wants their scientific results to be very useful and attractive to others.

SW: Where do you see your research leading in the future?

I guess that our research will be applied to reduce future earthquake hazards in China, and attract discussion on the formation of the Qinghai-Tibetan Plateau in academic circles.End

Xiwei Xu
Research professor in Earthquake Geology
Deputy Director
Institute of Geology
China Earthquake Administration
Beijing, Peoples Republic of China

KEYWORDS: SICHUAN, EARTHQUAKE.

 
 

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