MANILA, Philippines — Southern Mindanao experienced another strong tremor over the weekend as the geological fault lines off Davao Occidental continue to settle. The Philippine Institute of Volcanology and Seismology (Phivolcs) recorded a magnitude 4.9 earthquake in the waters off Sarangani.
State seismologists confirmed the early morning tremor was an aftershock tied to the powerful magnitude 7.8 mainshock that struck the exact same region a week prior on June 8.
The aftershock caused light to moderate shaking across nearby municipal towns but was calculated to have struck deep enough to avert major structural damage:
[ ADVISORY SEISMOLOGICAL RAW METRICS ]
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[ TEMPORAL & SPATIAL ORIGIN ] [ REVISED MAGNITUDE & DEPTH ]
• **Precise Timing:** The ground displacement was registered by regional • **The Downgrade:** Seismologists initially logged the shock
sensor stations at exactly **7:28 a.m.** • at a stronger magnitude 5.2 before officially downgrading
• **The Epicenter:** Located roughly 33 kilometers southeast of Balut • the metrics to a final **4.9 magnitude**.
Island—a volcanic island community under the jurisdiction of the • **Focus Depth:** The rupture originated at a tectonic depth
municipality of Sarangani, Davao Occidental. • of **33 kilometers** beneath the seabed.
Phivolcs mapped out how the seismic energy moved through the coastal borders of southern Mindanao, using both reported human perceptions (Perceived Intensity) and mechanical sensor networks (Instrumental Intensity):
[ EXPERIENCED SHAKING ENERGY GRADIENT ] │ ▼[ Intensity IV ] ──► **Moderately Strong:** Felt widely by residents indoors and outdoors across the island municipality of Sarangani, Davao Occidental. │ ▼[ Intensity III ]──► **Weak Shaking:** Reported by locals resting in Jose Abad Santos, Davao Occidental. │ ▼[ Intensity I ] ──► **Scarcely Perceptible:** Noted quietly by highly sensitive individuals inside high-rise buildings in General Santos City.
The automated seismic instruments stationed throughout Region XII and neighboring provinces registered the minor tremors as follows:
- Intensity II: General Santos City.
- Intensity I: Malapatan and Malungon, Sarangani; Tupi, South Cotabato; Santa Maria, Davao Occidental; and Digos City, Davao del Sur.
Phivolcs emphasized that because the energy release was a sub-5.0 aftershock at a moderate depth, no structural damages or destructive tsunami threats are expected from this specific event.
However, disaster mitigation offices maintain that coastal communities must remain highly alert. Fault systems adjusting after a massive 7.8 magnitude rupture can continue generating palpable aftershocks for weeks, keeping local response units on standby to ensure public safety.