Speech by Ma Zongjin, chairman of the National Wenchuan Earthquake Expert Committee

Ladies and gentlemen,

The 8-magnitude Wenchuan Earthquake, which occurred on May 12, 2008, has caused tremendous casualties, geological disasters and economic losses. As scientists, we feel greatly sorrowful and regretful and once again we intensively feel heavy responsibility shouldered for disasters prevention and reduction.

On May 21, the ninth meeting of the Earthquake Relief Headquarters of the State Council decided to set up the National Wenchuan Earthquake Expert Committee, which is made up of 30 experts. The experts were recommended by the China Earthquake Administration (CEA), the Ministry of Science and Technology (MOST) and the Ministry of Land and Resources (MLR), and according to principles as multi-departments, cross-discipline, combination of the elder, middle aged and young. After its establishment, the committee immediately coordinated with the field investigation and research team to conduct the field investigation and the analysis. The major task of the Expert Committee is to conduct the field investigation and evaluation of the earthquake, the geological structure and other aspects, to assist seismological departments in strong aftershock forecast and prevention of secondary disasters; to provide the scientific base for post-quake reconstruction planning through investigation and research; to do research on the causes, the laws and the tendencies of the Wenchuan Earthquake, and to offer scientific opinions for future earthquake prevention and disasters reduction based on material collection, analysis and research.

The Expert Committee has worked for over three months. Now I am going to tell you results of relevant work in four aspects.

The first aspect of work is the preliminary cognition of the Wenchuan earthquake occurrence mechanism.

The earthquake occurred in the Longmen Mountain main rupture, which is located in the middle section of the north-south earthquake belt in China . In terms of the regional tectonic background, in the early Cainozoic Era, the Indian Plate collided with the Asian-European Continent Plate, giving rise to the Tibetan Plateau. During the rise of plateau, the tectonic stress on the marginal zone along the two sides accumulated in a long term. According to the preliminary conclusion, the eastern side of the Tibetan Plateau along the Longmen Mountain tectonic zone extruded eastwards under the influence of the force of the Indian Plate to north-east, and pushed and blocked by the Sichuan Basin, it drove the sudden release of the massive energy on the Yingxiu-Beichuan Belt of the Longmen Mountain and induced the Wenchuan Earthquake.

The main shock occurred on the dextral obduction-type fault zone and the hypocenter depth was about 15km . After the field inspection of the earthquake and the geological structure and making analysis on various observation data, now it has been preliminarily confirmed that the east-northward Longmen Mountain that was gradually formed in the early Mesozoic Era has had three associated ruptures in parallel. The Yingxiu-Beichuan rupture on the Longmen Mountain was the main quake-causing rupture of the Wenchuan Earthquake.

With regard to the geophysical observation data of the Longmen Mountain and its surrounding areas in a few consecutive years, no outstanding abnormity had been identified before the earthquake and therefore no short-term and imminent forecast had been given. Although generations of geologists have been striving for providing definitive forecast, we are still far away from the goal. Chinese geoscientists together with those from other countries will face such a challenge. We believe that we will acquire the cognition of certain type earthquake one day, therefore gradually finding effective means to mitigate earthquake disaster.

The second aspect of work is the cognition of the aftershock development tendency.

As we all know, close attention is paid to the number, size and occurring place of aftershocks. In retrospect of earthquakes in mainland China in the past over 100 years, most of the aftershocks of the 10 earthquakes of over 7.8-magnitude have not exceeded magnitude 7.

As of the noon of Sept 1, the China Network of Earthquake Monitoring had recorded over 27,000 aftershocks, 112 days after the Wenchuan Earthquake. Among them, 8 aftershocks were above magnitude 6 and 39 aftershocks were above magnitude 5. The strongest was the 6.4-magnitude one hitting Qingchuan on the afternoon of May 25. The number of aftershocks as well as the intensity is still fluctuating considerably. The 5.6-magnitude, 6.0-magnitude and 6.1-magnitude aftershocks on July 24 near the Qingchuan County, which caused over 10 people dead or injured, urged long-term and intensified research of strong aftershocks.

After the analysis of the earthquake materials about mainland China from various perspectives, now the 5.12 Wenchuan Earthquake has still been basically identified as a main-aftershock type with low possibility of occurrence of aftershock above magnitude 6.5 in the earthquake-stricken area. However, according to analytical results of large earthquakes in the world and the aftershock sequence, it has been preliminarily confirmed that the active period of strong aftershock may last for a while. For the sake of safety, the earthquake department will keep on intensive monitoring upon the Wenchuan Earthquake-hit area and keep on relevant consultations as well for a while.

The third aspect of work is the investigation and evaluation of the earthquake and secondary disasters.

The destructive Wenchuan Earthquake induced massive landslide, collapse, debris flow and other geological disasters. According to the preliminary statistics, there have been over 12,000 occurrences of geological disasters, nearly 8,700 places with potential risk, and over 30 dangerous dammed lakes. After the earthquake, experts on earthquake study, geology and water conservation conducted an extensive investigation of the earthquake disaster and the secondary disasters, and gave constructive advices on disaster prevention and dammed lake treatment. The large number of secondary disasters caused by the Wenchuan Earthquake was mainly attributed to the large magnitude, the shallow hypocenter, so many active ruptures, high mountains, deep valleys and other natural factors.

The evaluation of severe natural disasters in an area of over 100,000 square kilometers is a heavy and hard task. Working with the State Development and Reform Commission (SDRC), the Ministry of Finance (MOF), the Ministry of Civil Affairs (MCA), the Ministry of Land and Resources (MLR), the China Earthquake Administration (CEA), and the National Bureau of Statistics (NBS), the Expert Committee has determined the categorizing principles of the type and range of disaster caused by the Wenchuan Earthquake and established the comprehensive index system of disaster situations, which are classified into areas hit by the significant earthquake, areas hit by the major earthquake, areas hit by the moderate earthquakes and areas slightly affected by the earthquake, by taking into account the number and ratio of the dead and the missing, collapsed houses and people transferred and resettled, the earthquake intensity, the risk of geological disasters, and especially the number of the dead and missing in the earthquake-stricken area and the average earthquake intensity.

So far, the evaluation of the type and range of the Wenchuan Earthquake disaster has been basically completed. According to the categorizing principle, there are 39 disaster areas hit by the significant earthquake or the major earthquake in Sichuan , 8 in Gansu and 4 in Shaanxi . In total, 51 counties (cities and districts) affected by the earthquake occupy an area of over 130,000 square kilometers. The precise measurement of the area that has been affected by secondary disasters induced by the Wenchuan Earthquake is still in progress.

The fourth aspect of work is the Expert Committee has contributed some constructive advices on the Wenchuan Overall Post-quake Recovery and Reconstruction Plan which is designed by the State Development and Reform Commission.

With regard to the characteristics of mountains and plateaus in the earthquake-stricken area, the reconstruction can be carried out by different areas and periods. In the mountain front area which was slightly damaged, the main task of reconstruction is to reinforce the damaged houses so as to recover the normal living and economic order. In the Longmen Mountain area which was severely damaged, the first task is to formulate the reconstruction plan comprehensively including multiple factors as local nature-bearing capacity, population scale, infrastructure layout, customs, demands of social and economic development, and to control the town size, away from the fault zones where geological disasters are likely to occur, and especially attach great importance to the lifeline project's disaster-proof capacity.

Up to now, the Expert Committee, supported by the China Earthquake Administration (CEA), the Ministry of Science and Technology (MOST), the Ministry of Land and Resources (MLR) and many other state departments, cooperated with the National Commission for Disaster Reduction (DCDR) and completed a few documents in early June, which have already provided references for earthquake recovery. These documents include the 8-magnitude Wenchuan Earthquake Intensity Diagram, the Earthquake-geological Disaster Atlas in the Area Hit by the Wenchuan Earthquake, the Atlas of Geological Disaster Investigation and Reports in the Main Disaster Region, the Technical Manual of Earthquake Relief in the Wenchuan Region, the Comprehensive Analysis and Evaluation Report of the Wenchuan Earthquake Disaster, and the Report of Comprehensive Management and Supporting Policy for the quake-hit area. The outputs above mentioned have already provided technical support post-quake recovery and reconstruction.

The national overall plan publicized for Wenchuan recovery and reconstruction is composed of 15 parts, namely, reconstruction base, overall requirement, space layout, urban and rural housing, city and township construction, rural construction, public service, infrastructure, industry construction, disaster prevention and reduction, ecological environment, spiritual home, policies and measures, reconstruction capital, planning implementation. According to the general guideline for the planning, the further planning of the ten plans dedicated to disaster reduction is still in progress.