| dc.description.abstract | The nature and extent of response of environmental factors and possible induced seismicity are investigated using the classifications based on the storm’s frequency and the accumulated cyclone energy (ACE) in the boreal summer season (June, July, August: JJA) in the West North Pacific (WNP) during 45 years (1977-2021) of the study period. A huge number of storms (42%) in the most cyclonically active ocean basin of the world (24 storms every year during 1977-2021) belong to boreal summer, in which around 32% directly cross the Pacific-Philippine Sea Plates’ boundary. The study uses Pearson’s correlation coefficient which is a measure of linear correlation between two variables, calculated by the ratio between their covariance and product of standard deviations. For extremely high TC activity years measured using storms frequency-based classification, the correlation between the frequency of TCs (TCs that cross the plate boundary) and earthquake events at the Pacific-Philippine plates boundary is strong (moderate) with correl. 0.73 (0.35), which keeps on increasing further from 0.75 (0.43), 0.75 (0.47) to 0.79 (0.66) with decreasing depths of 120 km (oceanic lithosphere thickness), 75 km (seismological lithosphere depth) to 30 km (mid-ocean ridges and transform margins have shallow earthquakes), respectively. For extremely high TC activity years measured using ACE-based classification, the above correlation for the TCs that cross the plates’ boundary improves by a huge 37%; correl. 0.48 (21%; correl. 0.52, 17%; correl. 0.55, 20% improvement; correl. 0.79, with earthquake depths 120 km, 75 km and 30 km, respectively), suggesting that the storm’s kinetic energy is significantly linked with the triggering the earthquakes. Being a huge size of natural phenomenon, the storms can trigger earthquakes even from a few hundred km away from the plates’ boundary, thus providing a bigger correlation (above 0.70) than the storms that directly cross the plates’ boundary (above 0.35), although it is not possible with ACE based classification because ACE is more associated with stronger storms which are more than three times less than the weaker storms. The Fisher’s Exact and Two-sided chi-square (χ2) tests reveal that both ACE and TC frequency-based techniques are interchangeable for the majority of studied parameters in boreal summer except cyclonic strength-based parameters as the ACE reflects storm’s kinetic energy. The earthquake magnitudes ranging from 4.1 to 4.9 on the Richter scale account for three-fourths (75%) of the triggered earthquakes at the plates’ boundary. Relative vorticity is found as the most sensitively linked with storms’ frequency. The role of middle-level tropospheric winds (850 hPa) is found in comparably more important for extremely low-TC activity years than in extremely high-TC activity years. Vertical shear is more crucial during extremely high-TC years than extremely low-TC years. The mutual dynamic and environmental connections among all environmental factors were discussed with their observed impact on storms frequency. Tropical cyclones (TC) and earthquakes both are the two most notorious natural hazards in the WNP-related regions, causing huge human and economic losses, while the extreme TC activity years link to flood, drought and water crises in the region. Hence, such a study is essential for the welfare of society, disaster risk-related agencies and researchers worldwide. | en_US |