Magnitude 5.1 earthquake near Tamblaka, Indonesia: IGG cable anomaly detected
What Happened
On July 12, 2026, at 16:20 local time, an earthquake with a magnitude of 5.1 occurred 27 km southeast of Tamblaka city, Indonesia. The depth of the seismic shocks was 10 km. This region is part of a highly seismically active zone, making it vulnerable to infrastructure damage, including submarine cables.
Cables in Zone
Within a radius of 500 km from the earthquake's epicenter, several large submarine cables are located. Among them:
- Indonesia Global Gateway (IGG) System (5300 km, RFS 2018, managed by Telin and Telkom Indonesia), nearest point - Bali (420.6 km).
- Mataram Kupang Cable System (MKCS) (1318 km, RFS 2011, Telkom Indonesia), nearest point - Bima (147.5 km).
- Indonesia Tengah Cable Systems (2641 km, RFS 2027, PT Jejaring Mitra Persada, Triasmitra), nearest point - Kawinda Nae (235.1 km).
- Link 3 Phase-1 (275 km, RFS 2003, XLSmart), nearest point - Kawinda Nae (235.1 km).
- Sape-Labuan Bajo-Ende-Kupang (474 km, RFS 2021, Moratelindo), nearest point - Ende (272.6 km).
- Denpasar-Waingapu Cable Systems (814 km, RFS 2019, Moratelindo), nearest point - Lombok (375.6 km).
- BALOK (60 km, RFS 2016, XLSmart), nearest point - Senggigi (381.1 km).
- Palapa Ring East (6300 km, RFS 2019, Indonesian Government, Moratelindo), nearest point - Baa (425.1 km).
What our measurements show
Among all the cables in the affected area, measurements showed a significant anomaly on the Indonesia Global Gateway (IGG) System. The round-trip time (RTT) increased from its baseline value of 55.5 ms to 207.7 ms, representing a jump of 152.1 ms (4.9σ above average). This may indicate temporary changes in the cable or its equipment characteristics.
Other cables such as Mataram Kupang Cable System (MKCS), Indonesia Tengah Cable Systems, and Palapa Ring East are currently operating normally without noticeable deviations from normal parameters.
Context and Risks
The region of Indonesia is a key node for submarine cables linking Southeast Asia with Australia and other parts of the world. Any infrastructure damage could lead to significant delays and disruptions in internet traffic, especially considering the high dependence of the region on these cables. The anomaly on IGG System may be related to temporary changes in the cable or its equipment characteristics, which requires further analysis.
If the issue persists or worsens, it may affect traffic routing in the region, increasing load on neighboring cables such as MKCS or Palapa Ring East.
Further Monitoring
We will continue to monitor RTT metrics and other parameters for all affected cables. Special attention will be given to IGG System to determine whether the detected anomaly is temporary or requires operator intervention to mitigate its effects.
Monitoring of neighboring cables, such as MKCS and Denpasar-Waingapu Cable Systems, will also be conducted to detect secondary effects caused by changes in network load.
