Search Results (2)

High-resolution seismic reflection profiles from the offshore segment of the Littoral Fault Zone (LFZ) near Nan’ao Island were analyzed to investigate fault activity and its potential link to the 1918 M7.3 earthquake. The data reveal a ~19 km-wide graben bounded by seaward- and landward-dipping normal faults, with fault-propagation folds and growth faults reaching the seafloor. Forward modeling of the fault-propagation fold indicates three discrete episodes of normal dip-slip displacement (~20 m per phase), separated by prolonged quiescent periods, suggesting episodic fault activity and seismic-scale strain accumulation. Despite the regional NW–SE compressional stress regime, active normal faulting is observed, implying vertical stress as the dominant driving force. A gravitational seismic model driven by upper crustal loading is proposed to explain both the fault motion and the down-draw tsunami observed during the 1918 event. These findings offer new insights into intraplate seismogenic mechanisms and associated hazards along the South China coast. Full article

Over the past 424 years, the Littoral Fault Zone (LFZ), located offshore of the South China coast, has experienced four destructive earthquakes (M ≥ 7). These events have resulted in an approximately 700 km seismic gap centered on the Greater Bay Area of China, home to over 70 million people. Despite previous studies on deeper crustal structures and geodynamic processes, the shallow structural architecture and recent tectonic activity of the LFZ within the seismic gap remain poorly understood due to limited offshore geophysical investigations. Here, we present new offshore geophysical data to explore the shallow crustal architecture and Holocene activity of the LFZ within this seismic gap. Multichannel seismic data reveal that the LFZ comprises a high-angle listric main normal fault along with several secondary normal faults. The main fault trends northeast and dips southeast in the shallow crustal architecture, serving as the basin-controlling fault in the north of the Pearl River Mouth Basin, with accumulated displacements ranging from 1.5 to 1.8 km. Furthermore, analysis of single-channel seismic data, and ¹⁴C dating results from the borehole, indicate that the most recent movement of the main fault occurred within the last ~10,000 years, with minimum vertical offsets of 1.2 m. Based on these findings, we emphasize the LFZ’s potential to generate a significant earthquake, estimated at M_w 7.0–7.5, within the inferred seismic gap. Our study highlights the potential earthquake hazard posed by the LFZ to the Greater Bay Area of China, while also providing valuable insights for the assessment of active submarine faults worldwide. Full article