Estimated likelihood of observing a large earthquake on a continental low-angle normal fault and implications for low-angle normal fault activity

Abstract

The lack of observed continental earthquakes that clearly occurred on low-angle normal faults (LANFs) may indicate that these structures are not seismically active or that these earthquakes are simply rare events. To address this, we compile all potentially active continental LANFs (24 in total) and calculate the likelihood of observing a significant earthquake on them over periods of 1-100 years. This probability depends on several factors including the frequency-magnitude distribution. For either a characteristic or Gutenberg-Richter distribution, we calculate a probability of about 0.5 that an earthquake greater than M6.5 (large enough to avoid ambiguity in dip angle) will be observed on any LANF in a period of 35 years, which is the current length of the global centroid moment tensor catalog. We then use Bayes' Theorem to illustrate how the absence of observed significant LANF seismicity over the catalog period moderately decreases the likelihood that the structures generate large earthquakes. Key Points GIS compilation of potentially active continental low-angle normal faults Fifty percent chance of large earthquake in 35 years if all LANFs are seismically active No observed quakes moderately decreases likelihood that LANFs are seismogenic © 2014. American Geophysical Union. All Rights Reserved.