Key Takeaways & Executive Findings
- •• Low-angle submarine landslides in the Pearl River Mouth Basin are primarily triggered by a combination of rapid sedimentation, high-pressure gas accumulation, and seismic events. • High-pressure gas acts as a long-term preconditioning factor by elevating pore pressures and reducing shear strength, predisposing the slope to failure. • Sea-level fluctuations control sedimentation patterns, leading to the formation of low-permeability strata that trap gas and promote overpressure. • Frequent or moderate earthquakes serve as the final trigger for local failure in an already destabilized slope.
Abstract
Low–angle submarine landslides pose a greater threat to offshore infrastructure compared to those with steep sliding angles. Understanding the preparation and triggering mechanism of these low–angle submarine landslides remains a significant challenge. This study focuses on a deformed low–angle submarine landslide in the shelf–slope break of the Pearl River Mouth Basin, South China Sea, integrating sedimentology, geophysics, and geotechnology to investigate potential failure mechanisms. The architecture and deformation characteristics of the submarine landslide were elucidated by analyzing multibeam and seismic data. Within the context of the regional geological history and tectonic framework, this study focuses on the factors (e.g., rapid sedimentation, fluid activity, and earthquakes) that potentially contributed to the submarine slope failure. Furthermore, a series of stability evaluations considering the effects of rapid sedimentation and earthquakes was conducted. Our findings indicate that the most probable triggering mechanism involves the combined effects of sedimentation controlled by sea–level fluctuations, high–pressure gas activity, and seismic events. The high–pressure gas, which acts as a long–term preconditioning factor by elevating pore pressures and reducing shear resistance within the sediment, accumulated beneath the upper and middle sections of the low–permeability stratum that was formed during sea–level rise and ultimately evolved into the sliding mass. The overpressure generated by gas accumulation predisposed the submarine slope to instability, and a frequent or moderate earthquake ultimately initiated local failure. This study enhances the mechanistic understanding of low–angle slope failures in the shelf–slope break zone and provides critical insights for assessing marine hazard risks.
1. Introduction
Submarine landslides are mass movements that occur widely in both shallow and deep–sea regions. These events not only pose significant risks to subsea cables, pipelines, oil platforms, and other marine infrastructure but also release tremendous amounts of energy that can generate tsunamis, thereby severely threatening the safety of coastal populations and their property [1–4]. For instance, the Grand Banks submarine landslide, located off the coast of Newfoundland, Canada, severed subsea communication cables, leading to a 13–hour communication blackout. The tsunami triggered by this event also caused the deaths of 27 people [5]. Due to the destructive risks posed by submarine landslides and the recent surge in global ocean development, submarine landslides have garnered widespread attention from both academic researchers and industrial communities.
One of the most significant characteristics of many submarine landslides, compared to terrestrial landslides, is their low sliding angles. According to statistics by Tanyas et al. [6], the maximum of terrestrial landslides is 85.0° and the mean sliding angle is 27.0°.
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Zhenghui Li, Cong Hu, Geetanjali Kishan Lohar, Xiujuan Wang, Duanxin Chen, Hanlu Liu, Devendra Narain Singh, Chaoqi Zhu, Yonggang Jia (2025). Potential failure mechanism of low–angle submarine landslides in shelf–slope break of Pearl River Mouth Basin, South China Sea. SinoTechIntel Verified Research. https://doi.org/10.1016/j.ijmst.2025.09.009
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Frequently Asked Questions
What are the main triggering mechanisms of low-angle submarine landslides in the Pearl River Mouth Basin?
The main triggering mechanisms are the combined effects of rapid sedimentation controlled by sea-level fluctuations, high-pressure gas activity, and seismic events. High-pressure gas acts as a long-term preconditioning factor by elevating pore pressures and reducing shear resistance, while frequent or moderate earthquakes ultimately initiate local failure.
How does high-pressure gas contribute to submarine slope instability?
High-pressure gas accumulates beneath low-permeability strata formed during sea-level rise, elevating pore pressures and reducing shear resistance within the sediment. This overpressure predisposes the slope to instability, making it more susceptible to failure when triggered by seismic events.
What role do sea-level fluctuations play in the formation of submarine landslides?
Sea-level fluctuations control sedimentation patterns, leading to the formation of low-permeability strata that can trap gas and promote overpressure. This creates favorable conditions for slope failure over time.
Why are low-angle submarine landslides considered more dangerous than steep ones?
Low-angle submarine landslides pose a greater threat to offshore infrastructure because they can occur on gentle slopes that are often overlooked, and they can travel long distances, potentially impacting larger areas and infrastructure.
What methods were used in this study to investigate the failure mechanisms?
The study integrated sedimentology, geophysics, and geotechnology, including analysis of multibeam and seismic data, and conducted stability evaluations considering the effects of rapid sedimentation and earthquakes.
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