Taiwan Earthquake Impacts APG and SJC2 Submarine Cables, RTT Deviations Confirmed
What Happened
On August 15, 2026, at 14:30:15 local time, an earthquake of magnitude 4.9 struck 63 km east-southeast of Ilan, Taiwan. The epicenter was located near the coast, raising immediate concerns about the submarine telecommunications cables that traverse this geologically active region. Taiwan's proximity to tectonic plate boundaries makes it particularly susceptible to seismic activity, and the coastal location of the epicenter heightened the potential for disruptions to critical underwater infrastructure.
Cables in Zone
Within a 500 km radius of the earthquake's epicenter lie several major submarine cables that play a vital role in connecting East and Southeast Asia with the global internet infrastructure. Among the most prominent are the Asia Pacific Gateway (APG) and Southeast Asia-Japan Cable 2 (SJC2). The APG cable, commissioned in 2016, spans 10,400 km and has a landing station in Toucheng, Taiwan, located just 66 km from the epicenter. The SJC2 cable, launched in 2025, measures 10,500 km and has an exit point in Fangshan, Taiwan, which is 298.1 km away from the earthquake's origin.
Other submarine cables in the vicinity include Topaz (operated by Google), Pacific Light Cable Network (PLCN), ORCA (Meta), New Cross Pacific (NCP), E2A, and Candle. These cables collectively form a dense network that supports high-speed data transmission across the Asia-Pacific region. GeoCables' monitoring systems confirmed that significant anomalies were detected specifically on the APG and SJC2 cables following the seismic event.
What Our Measurements Show
GeoCables' advanced monitoring systems recorded substantial changes in the performance metrics of the APG and SJC2 cables. On the APG cable, the base round-trip time (RTT) was measured at 75.1 ms prior to the earthquake. Post-event, the RTT surged to 146.9 ms, marking an increase of 71.8 ms - equivalent to a deviation of 6.2 standard deviations from the baseline. This sharp rise indicates a significant impact on data transmission efficiency.
Similarly, the SJC2 cable exhibited even more pronounced anomalies. Its RTT jumped from a baseline of 71.0 ms to 181.5 ms, an increase of 110.5 ms, corresponding to 11.4 standard deviations. These findings underscore the extent to which the earthquake affected the performance of these critical communication links.
Context and Risks
The region surrounding Taiwan serves as a crucial hub for submarine cable systems, facilitating data flow between East Asia, Southeast Asia, and the broader global network. Disruptions to cables like APG and SJC2 can lead to increased latency and reduced bandwidth for internet traffic across these regions. In scenarios where cable damage occurs, traffic may be rerouted to alternative systems such as PLCN or NCP, potentially straining their capacity and causing further delays.
Given the strategic importance of these cables, any prolonged disruptions could have ripple effects on global internet connectivity, impacting businesses, governments, and individuals who rely on seamless communication and data exchange. The earthquake highlights the vulnerability of submarine cable networks to natural disasters, emphasizing the need for robust monitoring and rapid response mechanisms.
Further Monitoring
GeoCables is actively monitoring the APG and SJC2 cables to assess whether the anomalies observed are temporary or indicative of underlying damage. Continuous data analysis will provide insights into the stability of these systems and guide any necessary interventions. Additionally, GeoCables is closely observing other cables in the area, including Topaz, PLCN, and NCP, to ensure that any potential changes in their performance are promptly identified and addressed.
Efforts to restore normal operations on affected cables will be tracked, and their impact on regional and global internet traffic will be evaluated. GeoCables remains committed to providing real-time updates and ensuring the resilience of submarine cable networks in this critical region.
