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Using advanced high-resolution seafloor and subsurface imaging, the research team mapped and analyzed the seafloor in unprecedented detail. Among the 1,500 landslide-related features identified, 63 exhibit substantial debris deposits, indicative of significant past slide events. The study identifies previously undocumented large-scale submarine landslides, such as those in the Catalina Basin, the Del Mar slide offshore of San Diego County, the San Gabriel slide complex offshore of Long Beach, and the massive San Nicolas slide, which spans 232 square kilometers, making it the largest known submarine landslide in the region.

The scientists' findings reveal that the failure of these submarine landslides is influenced by a combination of factors. The essential elements include: 

1. Significant Sediment Supply: Enhanced sediment deposition during periods of low sea levels plays a crucial role in providing the material that eventually fails and slides. 

2. Uplift and Steepening Along Faults: Tectonic activity along fault lines causes uplift and steepening of the seabed, creating conditions favorable for landslides. 

3. Earthquake Shaking: The seismic activity in southern California is a major trigger for these underwater landslides. Earthquakes induce shaking that destabilizes the sediment, leading to sudden and sometimes massive slide events.

This new understanding of the conditions required for submarine landslides underscores the need for comprehensive risk assessments for densely populated coastal regions such as those in southern California. As submarine landslides can directly impact human infrastructure and safety, this research is crucial for developing mitigation strategies and enhancing preparedness for potential underwater landslide-triggered tsunamis. 

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