Relationship between Earthquakes and Tropical Cyclones in the North Atlantic region

Atlantic region encompasses Caribbean Plate, which is characterized by different kinds of plate boundaries that include Transform and convergent types faults. Another interesting aspect of this region is the high occurrence rate of tropical cyclones during the months of July-November that peaks in September. Past studies have suggested that low pressure during an extreme tropical cyclone (TC) could trigger earthquake (EQ) due to stress imbalance over a fault and can result in its unclamping. However, those studies are limited and based on few events. In this study, we analyzed more than 50 years of EQ magnitude data provided by USGS and tropical cyclone TC data available at NOAA site. The methodology implemented in this work is a three step process: (a) investigating the correlation in long-term trends in both the data sets and (b) lead-lag correlation analysis to separate cause-effect relation, and (c) spatial overlap of the two events close to plate boundaries that are seat for EQ. Our results demonstrate increasing trend in the occurrence rate of TC and EQ in the Caribbean region. The correlation coefficient 0.8 is seen after the removal of 8 years periodicities that mitigate the effect of short term as well as inter-annual variability. Accumulated Cyclone Energy (ACE) index was calculated and different years are characterized as above and below normal seasons based on ACE index. The relationship between EQ occurrences for these two seasons is investigated and it shows that EQ activity during above normal TC season increases twice the amount compared to below normal TC periods. Such statistical studies can provide deep insights about the EQ triggering mechanism along with lithosphere-atmosphere coupling.