Spatial Based Integrated Assessment of Bedrock and Ground Motions, Fault Offsets, and Their Effects for the October-November 2002 Earthquake Sequence on the Denali Fault, Alaska

University Of Alaska Fairbanks Campus, Fairbanks AK

Investigators

Abstract

The M6.7 Nenana Mountain, Alaska earthquake that occurred on 23 October 2002 was followed by the M7.9 Denali Fault earthquake on 3 November 2002. The latter event is one of the largest strike-slip earthquakes to occur in the United States. Intense ground shaking lasted over 45 seconds. By comparison, the M7.1 1989 Loma Prieta Earthquake lasted 15 seconds. The Denali fault earthquakes caused ground failure and damage to several structures and highway bridges. However, considering the magnitude and associated energy release of the 3 November event, the damage was substantially less than expected. This action is to support a group of engineers and scientists to collect perishable data from the October-November 2002 earthquake sequence on the Denali Fault, Alaska. A nucleus of Alaskan scientists and engineers have agreed to cooperate with this research team and to satellite platform data that is stored for only a limited period of time. It builds on the findings of a geotechnical engineering reconnaissance team that visited the affected areas within days following the earthquake sequence. The objective is to archive bedrock motions, ground motions and fault offsets and their effects. It includes the accumulation of all strong motion records, satellite imagery, satellite remote sensing data, aerial and ground photographs, and structural response (both measured and anecdotal). Several interesting data sets will be archived, including ice cover, lateral movement of stream channels, landslides, avalanches, glacial fracturing, "felt" ground motions, and changes in water quantity and quality. The data sources may be spatially integrated to provide a comprehensive assessment of the bedrock and ground motions and fault offsets. The work of the reconnaissance team is a necessary prerequisite to understanding why the ground motions experienced did not substantially damage structures and the infrastructure. Furthermore, it will facilitate a comparison of Denali events with the 1989 Loma Prieta earthquake and the recent Kocelli and Dozce earthquake events in Turkey - all of which were associated with strike-slip faulting. Finally, the spatially integrated data will provide the basis for further research. For example, it can be used to model the observed landsliding and avalanches, changes in water quantity and quality, glacial fracturing, and the widespread liquefaction and lateral spreading that occurred along the Tok cutoff and Northway airport. An Advisory Board will help identify and provide access to data sources, and make recommendations regarding the format for presentation of the project results to insure their widespread use by other investigators. A webpage will be prepared to provide access to all data sets, analysis results, and digital photographs that are made available to the reconnaissance team, and to facilitate future research.