Earthquake M5.1 off Tamblak: Impact on Cables

What Happened

On July 12, 2026 at 16:20:25 local time, an earthquake of magnitude 5.1 occurred. The epicenter was located approximately 27 km southeast of Tamblak in Indonesia, at a depth of about 10 km. This event affected a region rich in submarine cable infrastructure, which provides connectivity both within the country and to international nodes.

Cables in Zone

Within a radius of 500 km from the earthquake's epicenter, there are eight submarine cable systems. Among them, the most significant ones are:

• Indonesia Global Gateway (IGG) System (5300 km, RFS 2018, operators Telin and Telkom Indonesia), nearest point - 420.6 km.
• Mataram Kupang Cable System (MKCS) (1318 km, RFS 2011, Telkom Indonesia), nearest point - 147.5 km.
• Indonesia Tengah Cable Systems (2641 km, RFS 2027, PT Jejaring Mitra Persada and Triasmitra), nearest point - 235.1 km.
• Link 3 Phase-1 (275 km, RFS 2003, XLSmart), nearest point - 235.1 km.

Other cables, such as Sape-Labuan Bajo-Ende-Kupang, Denpasar-Waingapu Cable Systems and BALOK, are also in the potential impact zone, but their distance from the epicenter exceeds 270 km.

What Our Measurements Show

The most notable anomaly was recorded on the Indonesia Global Gateway (IGG) System. The round-trip time (RTT) for this cable increased from its baseline value of 55.5 ms to 207.7 ms, representing an increase of 152.1 ms (4.9σ above the base line). This indicates significant disruption in the operation of the cable, likely caused by seismic waves or ground displacement.

Other cables, such as MKCS and Indonesia Tengah Cable Systems, are currently showing stable RTT within normal ranges. However, their proximity to the epicenter requires further monitoring.

Context and Risks

Indonesia is a key node for submarine cables in Southeast Asia. Earthquakes in this region can significantly impact global internet traffic, especially if damages affect major routes such as the IGG System. Increased RTT on this cable may slow down connectivity between Asian and Australian networks, as well as affect internal connections within Indonesia.

Furthermore, seismic activity highlights the vulnerability of cable infrastructure in areas with high tectonic activity. This requires prompt assessment of cable conditions and, if necessary, conducting repair work.

Further Monitoring

We will continue to monitor the condition of all eight cables in the earthquake zone. Special attention will be paid to IGG System, where a significant anomaly has already been recorded. Data on RTT for MKCS and other cables closest to the epicenter will also be analyzed.

In case of worsening metrics or confirmation of cable damage, we will update information promptly and provide recommendations for operators and market participants.