ALOS-2 Observations of the Earthquakes in the Philippines
(Cebu Island and Mindanao Island)

On September 30, 2025, a magnitude 6.9 earthquake struck off the northern coast of Cebu Island, the Philippines. Subsequently, on October 10, a magnitude 7.4 earthquake occurred off the southern coast of Mindanao Island.
As the Secretariat of Sentinel Asia, JAXA conducted emergency observations by ALOS-2 in response to both events. This article introduces the actions taken for each earthquake.

September 30, 2025: Earthquake on Cebu Island

At 23:00 JST on September 30, an earthquake struck in the norther coast of Cebu Island. In response, the Philippine Institute of Volcanology and Seismology (PHIVOLCS) and the Mines and Geosciences Bureau (MGB) of the Department of Environment and Natural Resources, both are Sentinel Asia members, activated Sentinel Asia.
Once the activation was made, JAXA conducted an emergency observation using the ALOS-2 satellite and provided data and analysis results according to the following timeline (Table 1).

Date	Time (JST)	Activity
Sep 30, 2025	23:00	Earthquake occurred in northern Cebu Island
Oct 1, 2025	15:00	Sentinel Asia was activated following requests from PHIVOLCS and MGB. JAXA began coordination for emergency observation by ALOS-2.
Oct 2, 2025	23:53	ALOS-2 conducted an emergency observation.
Oct 3, 2025	15:00	Damage Proxy Map (Figure 1) analyzed by the Earth Observatory of Singapore (EOS) was provided to Sentinel Asia.

Table1: Timeline of JAXA and Sentinel Asia response to the Cebu Earthquake on Sep 30, 2025

The timeline may vary depending on the factors such as available observation opportunities, the observation mode suitable for the disaster type, and the availability of pre-event imagery. In this case, the response was completed within approximately three days after the earthquake, allowing for timely information delivery.

Figure 1 shows the Damage Proxy Map generated by EOS using ALOS-2 data. Areas where surface changes were estimated between pre- and post-event images are shown in a color gradient from yellow to red. Regions in red indicate greater changes, implying a higher likelihood of damage to structures such as buildings, while yellow represents areas with smaller changes.

Figure 1: Damage Proxy Map analyzed by EOS using ALOS-2 data observed on October 2 night (JST)

The Embassy of Japan in the Philippines also shared activities about this event on their website (Figure 2) on October 7, 2025.

Figure 2: Website of the Embassy of Japan in the Philippines featuring the Cebu Earthquake activities done by ALOS-2

October 10, 2025: Earthquake on Mindanao Island

At 9:45 JST on October 10,2025, a large earthquake occurred off the southern coast of Mindanao Island. In this event, PHIVOLCS sent an emergency request and Sentinel Asia was activated.
JAXA subsequently coordinated and conducted an emergency observation with ALOS-2 at 23:53 JST on October 16, 2025.

Through Sentinel Asia, JAXA will continue to deepen its cooperation with both domestic and international members to assist in disaster response and mitigation.

<What is Sentinel Asia?>

Sentinel Asia is an international initiative aimed at supporting disaster management activities in the Asia-Pacific region through the utilization of space technology.
Sentinel Asia is aiming to enhance mitigation from natural disasters by sharing disaster-related information such as Earth observation satellite data on the Internet.
As of October 2025, there are 127 members from 30 countries including space agencies, research institutions, disaster prevention organizations.