The M_w 7.9 Wenchuan earthquake occurred on 12 May 2008 at 14:28 China standard time (06:28 UTC) in the middle of the day. People were caught by surprise because this region, along the edge of the Tibetan plateau, was not listed as a place with a high seismic hazard. Destruction was huge. More than four million inhabitants were left homeless. Casualties numbered more than 80,000 people, and there were major economic losses. This event was one of the deadliest earthquakes in China during the last few centuries, after the Haiyuan earthquake in 1920 and the Tangshan earthquake in 1976, which claimed 200,000 and 250,000 lives, respectively. The Wenchuan earthquake occurred a few months before the beginning of the 2008 Olympic games, held in Beijing, China, and the emergency response from the government of the Republic of China was massive. In part, for efficiency during this tremendous rescue effort, scientists had difficulty gaining access to the field for the first several months. Such difficulties have partly hampered deployment of temporary networks of survey equipment, such as GPS or seismic stations by international teams, as is often the case after a major earthquake.

Along with the M_w 7.7 Chi-Chi, Taiwan, earthquake in 1999 and the M_w 7.6 Kashmir earthquake in 2005, the 2008 Wenchuan earthquake is one of the largest continental thrust earthquakes with excellent field observations that was well recorded by a variety of geophysical networks. Hence, it remains a primary target for understanding strain-accommodation processes in a compressive environment. In addition, the Wenchuan earthquake, which occurred in the Longmen Shan range at the edge of the Tibetan plateau, has called into question certain viewpoints held by the scientific community. GPS results have repeatedly shown almost no signal across the Longmen Shan fault system, and for decades, many scientists have considered that only minor deformation could take place in the area. The Wenchuan earthquake has considerably challenged this belief.

Despite all the difficulties of access, the scientific community has put a considerable effort into understanding this event, which is in part reflected in the 34 papers presented in this special volume. It should be stressed that this earthquake has been a unique opportunity for the Chinese earth-sciences community to show the quality and the diversity of the teams active in China, and about 60% of the papers in this volume have a lead author who is Chinese...