The APEC Cooperation for Earthquake Simulations (ACES) held its 6th general symposium in Cairns, Australia from May 11–16, 2008. On the second day of the symposium, the importance of the ACES organization was underscored by the occurrence of the May 12, 2008 Wenchuan, China earthquake that killed more than 80 000 persons near the major metropolis of Chengdu, China. The 7th general symposium is to be held at Otaru, Japan during October 3–8, 2010, hosted by the government of Japan. The ACES organization was authorized by the Industrial Science and Technology Working Group of APEC at the 1997 Singapore meeting, in response to a resolution introduced by the government of Australia. As stated on the ACES home page, http://quakes.earth.uq.edu.au, earthquakes are one of the most costly and deadly natural disasters. APEC member economies are struck by the vast majority of the world's earthquakes and have a particularly high earthquake risk. This has resulted in more than 800 000 deaths in APEC member economies of the approximately 1.3 million deaths associated with earthquakes during the 20th century. During the 21st century, approximately 750 000 deaths have so far occurred as a result of earthquakes in India, Sumatra, Pakistan, China, and Haiti. The scientific method relies on the development of a theoretical framework or simulation model describing nature. While no such model exists for the complete earthquake generation process, conceptual developments in understanding earthquake physics, numerical simulation methodology and advances in High Performance Computing offer the possibility to develop such models. The APEC Cooperation for Earthquake Simulation (ACES) has capitalized on this opportunity and the complementary strengths of the earthquake research programs of individual APEC member economies. The ACES collaboration aims to develop numerical simulation models for the complete earthquake generation process, to assimilate new earthquake observations into such models, to foster collaboration between the relevant programs of participating member economies, and to foster the development of the required research infrastructure and research programs. Ultimately it is expected that these models will lead to progress in the difficult task of earthquake prediction and forecasting. Development of such simulation models represents a grand scientific challenge because of the complexity of phenomena and the range of scales involved from microscopic to global. These models are providing powerful new tools for studying earthquake precursory phenomena and the earthquake cycle. They have direct application to earthquake hazard studies and earthquake engineering, and the potential to yield spin-offs in sectors such as mining, geophysical exploration, high performance computing, material sciences, engineering and geotechnical studies. WG1: Microscopic simulation WG2: Scaling physics WG3: Macroscale simulation/Earthquake generation and cycles WG4: Macroscale simulation/Dynamic rupture and wave propagation WG5: Computational environment and algorithms WG6: Data assimilation and understanding WG7: Model applications to space-time earthquake hazard quantification The papers in this special volume of Concurrency in Computation represent the Proceedings of the 6 thgeneral symposium of ACES. The topics represented by these papers span many of the interests of ACES scientists and researchers, from the science of earthquakes, to forecasting, to supercomputer simulations. ACES is now moving into its second decade of existence. As there are now over 50 megacities worldwide having populations of 5 millions or more exposed to earthquake risk, many of them in Pacific Rim countries, it is expected that interest in these topics will only grow. Of the papers published in this volume, a number of groupings could be identified. Prominent among these groups were papers on the Load/Unload Response Ratio method, which has seen considerable development within the Chinese economy. Papers in this group include 1-3. Another group of papers is focused on the Pattern Informatics method for earthquake forecasting, including those in 4, 5. A number of papers dealt with numerical simulations of earthquake faults and numerical methods including visualization 6-12. A group focused on web services included 13-16. Other papers analyze specific earthquakes, including the Wenchuan earthquake that occurred on the second day of the meeting, May 12, 2008 17, 18 and earlier Chinese quakes 19, 20. Two final papers focused on tsunami simulation 21; and on testing earthquake forecasting methods 22. Together, these papers represent a broad look at the type of research that was discussed at the meeting. Many of these topics were brought into sharp focus by the occurrence of the devastating Wenchuan earthquake on May 12, and the terrible destruction and loss of life that resulted from this event. Representatives From the aces Member Economies: HULIN XING Australia KRISTY TIAMPO Canada XIANG-CHU YIN China HOW-WEI CHEN Chinese Taipei EIICHI FUKUYAMA Japan ANDREA DONNELLAN U.S.A.