On November 23rd 2022, a MW 6.0 earthquake occurred in direct vicinity of the MW 7.1 Düzce earthquake that ruptured a portion of the North Anatolian Fault in 1999. The Mw 6.0 event was attributed to a small fault portion of the Karadere segment that did not rupture during the 1999 sequence. We analyze the spatio-temporal evolution of the MW 6.0 Gölyaka-Düzce seismic sequence at various scales and resolve the source properties of the mainshock. Modelling the decade-long evolution of background seismicity of the Karadere Fault employing an Epistemic Type Aftershock Sequence model shows that this fault was almost seismically inactive before 1999, while a progressive increase in seismic activity is observed from 2000 onwards. A newly generated high-resolution seismicity catalog from 1 month before the mainshock until six days after created using Artificial Intelligence-aided techniques shows only few events occurring within the rupture area within the previous month, no spatio-temporal localization process and a lack of immediate foreshocks preceding the rupture. The aftershock hypocenter distribution suggests the activation of both the Karadere fault which ruptured in this earthquake as well as the Düzce fault that ruptured in 1999. First results on source parameters and the duration of the first P-wave pulse from the mainshock suggest that the mainshock propagated eastwards in agreement with predictions from a bimaterial interface model. The MW 6.0 Gölyaka-Düzce represents a good example of an earthquake rupture with damaging potential within a fault zone that is in a relatively early stage of the seismic cycle.

The main sources of the ambient seismic wavefield in the microseismic frequency band (peaking in the ~0.04-0.5 Hz range) are the earth’s oceans, namely wind-driven surface gravity waves (SGW) coupling oscillations into the seafloor and the upper crust underneath. Cyclones (e.g. hurricanes, typhoons) and other atmospheric storms are efficient generators of high ocean waves with complex but distinct microseismic signatures. In this study, we perform a polarization (i.e. 3-component) beamforming analysis of microseismic (0.05-0.16 Hz) retrograde Rayleigh and Love waves during major Atlantic hurricanes using a virtual array of seismometers in North America. Oceanic hindcasts and meteorological data are used for comparison. No continuous generation of microseism along the hurricane track is observed but rather an intermittent signal generation at specific oceanic locations along the track. Both seismic surface wave types show clear cyclone-related microseismic signatures and are consistent with a colocated generation at near-coastal or shallow regions, however the Love wavefield is comparatively less coherent. We identify two different kind of signals: a) intermittent signals that originate with a constant spatial lag at the trail of the hurricanes and b) signals remaining highly stationary in direction of arrival even days after the hurricane passed the presumable source region. This high complexity highlights the need for further studies to unravel the interplay between site-dependent geophysical parameters and SGW forcing at depth, as well as the potential use of cyclone microseisms as passive natural sources.

The main sources of the ambient seismic wavefield in the microseismic frequency band (peaking in the ∼0.04-0.5 Hz range) are the earth’s oceans, namely wind-driven surface gravity waves (SGW) coupling oscillations into the seafloor and the upper crust underneath. Cyclones (e.g. hurricanes, typhoons) and other atmospheric storms are efficient generators of high ocean waves with complex but distinct microseismic signatures. In this study, we perform a polarization (i.e. 3-component) beamforming analysis of microseismic (0.05-0.16 Hz) retrograde Rayleigh and Love waves during major Atlantic hurricanes using a virtual array of seismometers in North America. Oceanic hindcasts and meteorological data are used for comparison. No continuous generation of microseism along the hurricane track is observed but rather an intermittent signal generation at specific oceanic locations along the track. Both seismic surface wave types show clear cyclone-related microseismic signatures and are consistent with a colocated generation at near-coastal or shallow regions, however the Love wavefield is comparatively less coherent. We identify two different kind of signals: a) intermittent signals that originate with a constant spatial lag at the trail of the hurricanes and b) signals remaining highly stationary in direction of arrival even days after the hurricane passed the presumable source region. This high complexity highlights the need for further studies to unravel the interplay between site-dependent geophysical parameters and SGW forcing at depth, as well as the potential use of cyclone microseisms as passive natural sources.