On Monday Night a Shallow M5.5 FORESHOCK struck in the South China Sea near Aparri (The Philippines).

Written by Earthquakelist.org on April 27th, 2025. Last updated May 17th, 2025.

In the night of Monday April 28th, 2025, a shallow and significant M5.5 foreshock hit in the South China Sea 99 kilometer from Aparri, The Philippines. Shaking may have been felt by a total of 3.3 million people.

Earthquake Summary

This earthquake hit under water in the South China Sea, 30 kilometers (19 mi) off the coast of The Philippines, 99 kilometer north-northwest of Aparri in Cagayan Valley. The center of this earthquake had a very shallow depth of 10 km. Shallow earthquakes usually have a larger impact than earthquakes deep in the earth.

Date and Time:	Apr 28, 2025 12:54AM (Manila Time) - Apr 27, 2025 16:54 Universal Time.
Location:	99 km NNW of Aparri, Cagayan Valley, The Philippines. Coordinates 19°8'19"N 121°11'14"E.
Map:	Map of area around epicenter. Click to open in Google Maps.
Magnitude:	MAG 5.5 Detected by 24 stations. Maximum Error Range ±0.063 .
Depth:	10 km (6 mi) A very shallow depth.
Max. Intensity:	VI Strong On the Modified Mercalli Scale.
Tsunami Risk:	Low tsunami risk Earthquakes under MAG-6.5 do not usually cause tsunami's. Always stay cautious - More info here.

Minimal impact predicted

Based on scientific estimates by the US Geographic Survey (USGS), the risk of high fatalities for this earthquake is classified at level GREEN (low). They expect an 65% likelyhood of between 0 and 1 fatalities, and a 96% chance that the number of fatalities falls no higher than 10.

The USGS classifies the economic impact of this earthquake at level GREEN (low). They expect an 65% likelyhood of between 0 and 1 million US Dollars in economic damage and impact, and a 96% chance that the economic impact of this earthquake falls no higher than 10 million USD.

Roughly 3.3 million people exposed to shaking

The USGS has published a report estimating the number of people exposed to this earthquake. Acoording to their analysis, roughly 3.3 million have been exposed to shaking at an MMI level of II or higher.

The highest earthquake impact level for this earthquake is VI, which corresponds with strong shaking and probably light damage. Roughly 10 people are expected to be exposed to this level. Intensity level III was experienced by the majority of people (around 2.6 million). In their region, weak shaking and probably no damage can be expected. All exposure to shaking was within the borders of The Philippines .

People	MMI Level	Shaking	Damage
0	I	Not noticable	None
48,020	II	Very weak	None
2,570,000	III	Weak	Probably none
707,300	IV	Light	Likely none
960	V	Moderate	Very light
10	VI	Strong	Light
0	VII	Very Strong	Moderate
0	VIII	Severe	Moderate to heavy
0	IX	Violent	Heavy
0	X	Extreme	Very heavy

Nearby towns and cities

This earthquake may have been felt in The Philippines . The closest significant population center near the earthquake is Aparri in Cagayan Valley, The Philippines. Aparri is located 99 kilometer (62 mi) north-northwest of the epicenter. The intensity of shaking and damage in Aparri is estimated to be around level IV on the Modified Mercalli Intensity scale (light shaking, likely no damage).

Multiple large cities are in proximity of today's earthquake. Laoag is located 122 km to the south-southwest and experienced an intensity of IV (light shaking, likely no damage). Tuguegarao is located 179 km to the south-southeast and experienced an intensity of III (weak shaking, probably no damage). Santiago is located 275 km to the south (intensity unknown, possibly low).

An overview of nearby towns and cities is available in the overview below. If places don't have intensity data available, it likely means the experienced impact in those places was fairly small.

Overview of nearby places

Cities and Towns around the epicenter of this earthquake.
Distance	Place	Intensity (MMI)
99 km (62 mi) SSE from epicenter	Aparri Cagayan Valley, The Philippines.	IV Light
122 km (76 mi) SSW from epicenter	Laoag Ilocos, The Philippines.	IV Light
124 km (77 mi) SSW from epicenter	San Nicolas Ilocos, The Philippines.	IV Light
137 km (85 mi) SSW from epicenter	Batac City Ilocos, The Philippines.	IV Light
174 km (108 mi) SSE from epicenter	Solana Cagayan Valley, The Philippines.	III Weak
179 km (111 mi) SSE from epicenter	Tuguegarao Cagayan Valley, The Philippines.	III Weak
187 km (116 mi) S from epicenter	Tabuk Cordillera, The Philippines.	III Weak
193 km (120 mi) SSW from epicenter	Vigan Ilocos, The Philippines.	III Weak
200 km (124 mi) SSE from epicenter	Cabagan Cagayan Valley, The Philippines.	III Weak
229 km (142 mi) SSE from epicenter	Roxas Cagayan Valley, The Philippines.
233 km (145 mi) SSE from epicenter	Ilagan Cagayan Valley, The Philippines.
254 km (158 mi) S from epicenter	San Mateo Cagayan Valley, The Philippines.
256 km (159 mi) SSW from epicenter	Santa Maria Ilocos, The Philippines.
257 km (160 mi) SSW from epicenter	Tagudin Ilocos, The Philippines.
257 km (160 mi) S from epicenter	Mankayan Cordillera, The Philippines.
264 km (164 mi) S from epicenter	Ramon Cagayan Valley, The Philippines.
268 km (167 mi) SSE from epicenter	Alicia Cagayan Valley, The Philippines.
269 km (167 mi) S from epicenter	Diadi Cagayan Valley, The Philippines.
275 km (171 mi) S from epicenter	Santiago Cagayan Valley, The Philippines.
291 km (181 mi) S from epicenter	Solano Cagayan Valley, The Philippines.
293 km (182 mi) S from epicenter	Baggabag B Cagayan Valley, The Philippines.
295 km (183 mi) SSW from epicenter	San Fernando Ilocos, The Philippines.
296 km (184 mi) S from epicenter	Bayombong Cagayan Valley, The Philippines.

Earthquake Intensity Map

The intensity in shaking and damage by this earthquake is illustrated through the map below. The highest intensity measured for this earthquake is VI.

I Not felt

II Weak

III Weak

IV Light

V Moderate

VI Strong

VII Very Strong

VIII Severe

IX Violent

X Extreme

Earthquake Intensity Map based on Shakemap Data provided by USGS.

Shaking reported by 3 people

People that feel an earthquake may report their experience to the US Geographic Survey. Currently, 3 people have reported shaking in 2 places in Philippines.We keep updating this article as more ground reports become available. You may report that you felt this earthquake here.

Places with most reports:

Namuac, Cagayan Valley, Philippines: 2 people.
Bangui, Ilocos, Philippines: 1 person.

This is likely a foreshock

This earthquake was followed by a stronger MAG-5.6 earthquake, classifying this earthquake as a foreshock.

Overview of foreshocks and aftershocks

Detected MAG2.5+ earthquakes within within 100km (62 mi), that occurred in the three days before and after the main shock.
Classification	Magnitude	When	Where
Foreshock	M 3.0	6 hrs earlier Apr 27, 2025 07:48PM (Manila Time)	69 km (43 mi) N from Main Shock.
Foreshock This Earthquake	M 5.5	24 mins earlier Apr 28, 2025 12:54AM (Manila Time)	8 km (5 mi) SSE from Main Shock.
Main Shock	M 5.6	Apr 28, 2025 01:18AM (Manila Time)	-
Aftershock	M 3.2	9 hrs later Apr 28, 2025 09:54AM (Manila Time)	5 km (3 mi) NNE from Main Shock.
Aftershock	M 3.0	2 days later Apr 30, 2025 04:25AM (Manila Time)	16 km (10 mi) NNE from Main Shock.

More earthquakes coming?

The risk of aftershocks decreases rapidly over time. Usually, aftershocks are at least one order of magnitude lower than a main shock.

It's always adviced to be cautious of the risk of a larger shock following any significant earthquake, however this risk is fairly small. There is a roughly 94 percent change that no larger main shock will follow in the days following this earthquake.

Read: How to Stay Safe during an Earthquake (cdc.gov).

Earthquakes like this happen often in the region

Earthquakes of this strength are very common in the region. This is the strongest earthquake to hit since December 30th, 2024, when a 5.5 magnitude earthquake hit 83 km (52 mi) further south-southwest. An even stronger magnitude 7 earthquake struck on July 27th, 2022.

In total, 20 earthquakes with a magnitude of 5.5 or higher have been registered within 300km (186 mi) of this epicenter in the past 10 years. This comes down to an average of once every 6 months.

Low tsunami risk

DISCLAIMER: We strongly suggest to closely monitor advice from local authorities with regards to tsunami risks. Our analysis is based on automatically collected data from external sources, and these might contain mistakes. In addition, earthquakes can cause landslides that may lead to a tsunami, or be a followed by another, potentially stonger, earthquake.

Based on early data it appears this earthquake was not strong enough (lower than MAG-6.5) to be likely to cause destructive tsunami's. However this earthquake appeared to have hit at a shallow depth under sea, so stay cautious and monitor advice from local authorities.

Tsunami Risk Factors

Factor	Under Sea?	MAG-6.5 or stronger?	Shallow depth?
Explanation	Almost all tsunami's are caused by earthquakes with their epicenter under sea or very near the sea. However stay cautious in coastal areas as earthquakes on land may cause landslides into sea, potentially still causing a local tsunami.	Under MAG 6.5: Very unlikely to cause a tsunami. MAG 6.5 to 7.5: Destructive tsunami's do occur, but are uncommon. Likely to observe small sea level changes. MAG 7.6+: Earthquakes with these magnitudes might produce destructive tsunami's.	Most destructive tsunami's are caused by shallow earthquakes with a depth between 0 and 100km under the surface of the earth. Deeper tsunami's are unlikely to displace to ocean floor.
This Earthquake	This earthquake appears to have struck under the sea.	Not this earthquake. This earthquake had a magnitude of 5.5. Earthquakes of this strength are unlikely to trigger a tsunami.	This earthquake occurred at a depth of of 10 km (6 mi). Earthquakes this shallow could trigger a tsunami.

Sources

Last updated 17/05/25 19:08 (). This article contains currently available information about the earthquake and is automatically composed. We continue to update this article up to a few days after the earthquake occurred.