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Abstract Despite advancements in understanding the rupture processes and surface deformations of the 2023 Türkiye earthquake doublet, their seismogenic mechanisms remain elusive. Here, we determined the three-dimensional fine-scale seismic and porosity structures in the rupture zones. We find that the first Mw 7.8 earthquake occurred in a brittle or near-brittle structure zone with low porosity and fluid saturation, offering a potential condition for brittle failure with supershear rupture. By contrast, the second Mw 7.6 quake initiated in a ductile belt characterized by high porosity and fluid saturation, explaining the observed sub-shear rupture behaviors. The former induces large decreasing normal stress, thus opening the Çardak fault, accelerating the migration of saturated fluids towards the fault zone through intra-crustal faults and extended cracks, increasing pore pressure, and delaying triggering a second earthquake. Our findings reveal the diverse seismogenic mechanisms of the Türkiye earthquake doublet, suggesting that fluid intrusion may have played a crucial role in triggering an earthquake.
Wang et al. (Tue,) studied this question.