Spatial and temporal study of the seismicity of the hypocentral region of the Great 1964 Alaskan Earthquake

• Main Author: De La Pena, Alejandro
• Format: Text
• Language: English
• Published: ScholarWorks@UTEP 2007
• Subjects: Geology|Geophysics; Beck; Christensen; Pacific; Yakutat; Alaska
• Online Access: https://scholarworks.utep.edu/dissertations/AAI1444084

In March 28, 1964, the largest earthquake (9.2 MW) in North America occurred in south-central Alaska (SCA). The epicenter of this great earthquake was in Prince William Sound (PWS) (Figure 1). The earthquake occurred as a result of underthrusting of the Pacific plate and Yakutat Block beneath the North American plate along an 800 km long stretch of the Alaska subduction zone (Christensen and Beck, 1994). This study focuses on relocating events that occurred in the time period from 1989 to 2001 in a region of 100 by 165 km surrounding the epicenter of the 1964 mainshock. It also includes waveform modeling of two events (Mw 6.5 & 6.4) that occurred in 1983 east of the mainshock. The relocation process was conducted using a double difference relocation program (HypoDD, Waldhauser, 2001) that better defines patterns of seismicity. The relocation results were compared to gravity and magnetic data of the area. The results suggest that the main clusters of seismicity are concentrated in the Wadati-Benioff zone, and along major faults that represent the boundaries between accreted terranes. Body waveform modeling results better constrained the depths of the 1983 events to 30-31 km and provided information about their source parameters. Their source time functions showed no clear effects of directivity. Their focal mechanisms confirmed that the events had occurred within the subducting slab, and their stress drops were consistent with other intraplate events.