| dc.description.abstract | Subsurface microorganisms have been estimated to constitute 1/5 of the global biomass, quantitatively playing an important role in biogeochemical cycling. On the other hand, earthquake is a common phenomenon of stress release in the crust. Seismic ruptures cause comminution of materials in the fault zone and drive different physicochemical actions. To date, the studies related to the interaction between microorganisms and earthquake focused on the change of microbial diversity and community structure by analyzing water sample around faults before and after an earthquake. However, the effects of seismic ruptures on microbial proliferation have never been investigated. In this study, by using a purpose-built sample holder, we applied rotary shearing on the water-saturated kaolinite amended with two kind of bacterial strains, Shewanella oneidensis and Pseudomonas putida, which are commonly found in various environments, to investigate the potential of microbial survival after seismic ruptures. To simulate fault propagation, the water-saturated kaolinite was deformed at a seismic slip rate of 1 m/s for a total slip of 3 m (~M7 earthquake) or 10 m (~M7.5 earthquake) under a normal stress of 10 MPa. Results showed that compression damaged the cells in different levels to strains. Intact and viable cells decreased by tens of percent and orders of magnitude after shearing, respectively. Based on the fault behavior and mechanism in publication, we infered that when an earthquake ruptures: (1) The initial comminution greatly reduce the number of cells. And the following weakening mechanism driven by thermal pressurization enlarge the gaps between clay particles, making more intact cells to be preserved and survived. (2) The strains can survive an earthquake of magnitude 7. (3) With an earthquake of magnitude 7.5, temperature raised during shearing imposes great stress on these strains, leading to the extinction. This study demonstrates the survival and extinction of microorganisms in the fault zone after a seismic rupture, and suggests that thermal pressurization is the mechanism for the survival of microorganisms. | en_US |