Detection of Repeating Earthquakes Along the Northern Mariana Shallow Thrust Zone

Abstract:

The seismogenic character of the Northern Mariana Thrust Zone is unknown because of the absence of large historical megathrust earthquakes and the lack of appropriate geodetic data. Subduction seismicity in the Northern Mariana forearc shows clustering of events along strike and with depth. To further investigate the seismogenic characteristics of the region, we search for repeating earthquakes along the shallow thrust zone. Using the 2003-2004 Subduction Factory and 2012-2013 Mariana Trench Imaging Experiments, a cross correlation detection scanner is implemented to find repeating earthquakes. Template earthquakes are chosen from seismicity located within clusters along the shallow thrust zone and compared with continuous data from nearby ocean bottom seismometers using both conventional and subspace correlation detection methods. Preliminary results from scanning the 2003-2004 deployment have identified several families of repeating events. Many of these groups consist of repeating events that occur within a short time frame of the template event. In particular, several families have been detected in conjunction with the July 15, 2003 magnitude 5.1 earthquake, indicating detection of aftershock sequences. Repeating events that occur throughout the 2003-2004 yearlong deployment have also been detected, suggesting stable sliding of the plate with small asperities causing these repeating events. Further work may allow delineation of stable sliding regions as well as evaluation of the possible effects of several seamounts which are subducting within the study region.