Using GeoGateway Data to Explore Deformation in the Cajon Pass Region

Megan A. Mirkhanian, Lisa Grant Ludwig, Andrea Donnellan, Jay W. Parker, & Robert A. Granat

Submitted August 15, 2018, SCEC Contribution #8833, 2018 SCEC Annual Meeting Poster #258 (PDF)

GeoGateway ( is a web map-based science gateway supported by NASA’s ACCESS program. A goal of GeoGateway is to expand the utility of NASA’s geodetic imaging data products by making them easy to access, analyze, and interpret. The objective of this project is to use GeoGateway to explore tectonic deformation associated with recent seismic activity in the Cajon Pass region. The area can be investigated using the Line-of-Sight (LOS) tool which allows us to easily select UAVSAR (Uninhabited Aerial Vehicle Synthetic Aperture Radar) Interferometry data and Global Positioning Satellite (GPS) data via GeoGateway. The Cajon Pass, a fault junction between the San Andreas Fault and San Jacinto Fault (SJF), contains many critical lifeline facilities, and is bounded by the San Bernardino and San Gabriel mountain ranges in southern California. The Cajon Pass is being investigated as a possible “Earthquake Gate”, where areas of fault complexity halt earthquake ruptures depending on if the gate is “opened” or “closed.” Identification of interseismic strain accumulation and co-seismic slip on faults near Cajon Pass is important for understanding fault system behavior and mitigating damage from earthquakes. We used GeoGateway to search for deformation associated with the 29 December 2015 Mw4.4 Devore earthquake (epicenter 34.191°N 117.413°W) which occurred at depth of ~7.0 km on the SJF, to assess if such deformation can be identified. Using LOS tool for UAVSAR interferometric data display, we found measurable change, but the anthropogenic and hydrologic signals appears to be larger than the tectonic signal, making it difficult to identify tectonic deformation. However, there might be a slight persistent uplift of about 1 mm a year in the Cajon Pass. An elastic forward model of the earthquake shows that the event is too small and far from the Cajon Pass to produce measurable surface deformation, however the observed regional uplift deformation and the occurrence of the earthquake may be reflective of the state of stress of the crust in that region and long-term tectonic motion.

Mirkhanian, M. A., Grant Ludwig, L., Donnellan, A., Parker, J. W., & Granat, R. A. (2018, 08). Using GeoGateway Data to Explore Deformation in the Cajon Pass Region. Poster Presentation at 2018 SCEC Annual Meeting.

Related Projects & Working Groups
San Andreas Fault System (SAFS)