A recent study has delved deep beneath the Pacific coast of Mexico, exploring the complex dynamics of megathrust earthquakes and slow earthquakes. This investigation centers on the Guerrero seismic gap, where the Cocos plate is subducting beneath the North American plate. Through advanced three-dimensional thermomechanical modeling, researchers have uncovered insights about temperature conditions and dehydration processes at the plate interface, which could play significant roles in seismic activity.
The Cocos plate, which is currently descending at approximately 6.6 centimeters per year along the Middle America Trench, has long been associated with notable megathrust earthquakes. Significant events, including those of 1985, 1995, and 2017, have shaped the seismic history of the area. Meanwhile, the Guerrero seismic gap, identified as having been dormant for over 100 years, poses questions about the stress accumulation and potential catastrophic quakes.
To understand the seismic phenomena within this region, the researchers conducted extensive 3-D thermomechanical numerical simulations. These simulations estimate various temperature fields along the slab surface, particularly where megathrust earthquakes are likely to occur. The findings estimate the surface temperature to be between 200 and 400 °C at these locations, providing foundational knowledge for evaluating seismic risk.
Interestingly, long-term slow slip events (L-SSEs) occur with a recurrence interval of around four years. The researchers found these slip events correspond to temperature ranges between 350 and 550 °C, particularly outside the Guerrero seismic gap. Within the gap, the largest observed slip was approximately 14 centimeters, occurring at updip limit temperatures around 350 °C. Such temperature conditions suggest unique geological dynamics at play within this seismic anomaly.
Focusing on regions affected by tectonic tremors, the team reported heating estimates between 500 and 570 °C for seaside swarms and even higher temperatures ranging from 600 to 700 °C for inland swarms. This thermal profile highlights substantial differences across the Guerrero seismic gap, where acute tectonic activity is evident.
The comprehensive examination of varying temperatures across different seismic events enriches our comprehension of the broader tectonic interactions present. For example, tectonic tremors have been closely monitored, with swarms aligning nearly parallel along the subduction arc. These observations could facilitate improved earthquake forecasting and preparation strategies along densely populated coastal regions.
The Guerrero seismic gap's unique geological characteristics were revealed through detailed modeling, estimating the effective friction coefficient, the downdip limit of the high viscosity region, and the viscosity within the high viscosity region to be 0.0085, 50 km, and 1.0 × 1025 Pa s, respectively. The simulated model provides enhanced clarity to established geological hypotheses by determining newly refined parameters for earthquake behaviors.
Despite gaps in our current knowledge, findings indicate phase transitions and dehydration gradients associated with the subduction of oceanic crust and ultramafic rock. Such findings indicate the dynamic interplay between temperature and seismic activities could be integral to generating future slow earthquakes.
Overall, this study provides significant insight beneficial for earthquake scientists and public safety officials monitoring seismic activities. It emphasizes the influence of factors such as temperature and dehydration directly influencing seismic slip behavior and slow earthquakes. Understanding such dynamics within subduction zones can aid future efforts to assess and mitigate earthquake risks associated with the Guerrero seismic gap.
Researchers maintain the importance of continual surveillance of the region to track these fluctuations and to anticipate future seismic events adequately. The insights gleaned from thermomechanical modeling may not only aid scientists but help authorities prepare communities for potential natural disasters stemming from seismic activity.