To be featured in Seismological Research Letters and The Conversation
A recently published paper by Drs. Goebel & Shiraei professors at UofM's Center for Earthquake Research and Information and Virginia Tech, respectively, focuses on human induced earthquakes close to the San Andreas fault in central California, an area that was previously only famous for natural earthquakes. Induced seismic events have been a serious concern in the central and eastern United States and earthquake rates have increased by a factor of 50 in some places.
California was thought to be largely free of such unnatural earthquakes, meaning that oilfield operations and tectonic faults apparently coexisted without any issues. However, the research now shows that human induced earthquakes in California can be masked by frequently occurring natural events. Goebel and Shirzaei analyzed satellite radar-images acquired by the Sentinel-1A/B satellites between 2016 and 2020 and found that the surface above the San Ardo oilfield experienced consistent uplift of up to 1.5 cm/yr. This uplift is a clear indication of fluid pressure imbalance in parts of the oilfield which may exert stresses on the surrounding tectonic system. Fluid injection and earthquakes in San Ardo are highly correlated over more than 40 years. Surprisingly, earthquake activity extends out to 24 km from the oilfield. Such large distances are similar to the large spatial footprint of injection in Oklahoma. The observations in central California revealed several conditions that elevate injection-induced seismic hazard namely (1) fluid injection operations directly above crystalline basement rocks, (2) high-rate, field-wide injection into permeable zones, and (3) the presence of tectonically stressed faults. These criteria may help guide fluid-injection operations and safer energy production in the future.
For more information on this research, contact Goebel at thgoebel@memphis.edu.