Earthquake hazards
PHIVOLCS names six hazards an earthquake brings: ground rupture, ground shaking, earthquake-induced landslides, liquefaction, tsunami, and the coast rising or sinking. Shaking is the one most people feel. Which of the other five reach you depends on where you are: on an active fault, on a slope, on low wet ground near water, or on the coast.
What to do before an earthquake is on the earthquake preparedness guide, and what to do during and after is on the lindol page. This page is about what the earthquake does to the ground.
Written for the Philippines. In an emergency here, the number is 911.
The six, and where each one happens
The numbers in the drawing match the table. The drawing places each hazard where PHIVOLCS says it occurs. It is a sketch of the terrain and is not to scale.
| Hazard | What it is | Where PHIVOLCS puts it |
|---|---|---|
| 1. Ground rupture | The ground surface breaking and shifting along an active fault, so the cracks can be seen. | Along active faults. |
| 2. Ground shaking | The up and down or sideways motion of the ground as seismic waves pass through it. | Widespread when it is strong. Generally stronger near the epicenter. |
| 3. Earthquake-induced landslide | Soil, rock and debris moving downslope because of the shaking. | Slopes, and steeper slopes most of all. |
| 4. Liquefaction | Loose, wet, sandy ground behaving like a liquid while it shakes. | Lowlands near water: beaches, deltas, riverbanks, reclaimed land and floodplains. |
| 5. Tsunami | A series of waves. An undersea earthquake is one of the causes PHIVOLCS lists. | Every coastal area in the Philippines, for a local tsunami. |
| 6. Coastal uplift or subsidence | The coast itself moving up or down along a fault or subduction zone. | Coasts above the fault or subduction zone that moved. |
Source: PHIVOLCS, Earthquake Hazards. Read 23 October 2026.
Ground shaking
PHIVOLCS defines ground shaking as the up and down or sideways motion of the ground caused by seismic waves from an earthquake. It is generally stronger near the epicenter and weaker farther away. How strong it was at a place is its intensity, which the Philippines measures on the PHIVOLCS Earthquake Intensity Scale. The energy the earthquake released is its magnitude, a different number.
Strong shaking can damage and collapse buildings, and PHIVOLCS says collapsed structures and falling and toppled objects can lead to injuries and death. Fires can follow when gas tanks, fuel pipelines and electrical wires are damaged or flammable liquids spill. Strong shaking can also trigger landslides in mountainous areas and liquefaction in low-lying ones. Where the ground is limestone, it can make sinkholes collapse.
The example PHIVOLCS gives is the Hyatt Terraces Hotel in Baguio City, which collapsed in the Luzon earthquake of 16 July 1990.
The ten intensity levels are set out, in PHIVOLCS's words, on the magnitude and intensity page. What to do while the ground is moving is on the duck, cover and hold page.
Source: PHIVOLCS, Earthquake Hazards. Read 23 October 2026.
Ground rupture
Ground rupture is the hazard that belongs to active faults. PHIVOLCS describes it as the displacement of the ground surface along an active fault, leaving fracturing or cracking that can be seen.
PHIVOLCS gives two Philippine examples:
- The magnitude 7.8 earthquake of 16 July 1990 on the Digdig segment of the Philippine Fault, which produced a ground rupture 125 kilometers long, from Dingalan, Aurora to Kayapa, Nueva Vizcaya. Rice paddies in Imugan, Nueva Vizcaya were shifted sideways.
- The magnitude 7.2 Bohol earthquake of 15 October 2013, where the ground in Brgy. Anonang, Inabanga rose by about 2 meters along the North Bohol Fault.
What an active fault is, the three ways a fault moves, and how to find the nearest one to your house are on the types of faults page. The fault under Metro Manila has a page of its own.
Source: PHIVOLCS, Earthquake Hazards. Read 23 October 2026.
Earthquake-induced landslides
This is the downslope movement of soil, rock and debris set off by the shaking. PHIVOLCS says steeper slopes are more prone to it, because gravity pulls harder on them.
The part worth knowing after an earthquake: landslides can happen during the main shock, and tension cracks can open on the slope at the same time. PHIVOLCS says those cracks are a sign of a landslide still to come, which a later earthquake or heavy and prolonged rain can set off.
PHIVOLCS divides a landslide into three parts: the source zone where the slope first failed, the transport zone the material travels down, and the depositional zone where it settles. The harm it lists is houses and roads buried along the path, communities cut off by blocked roads, and rivers dammed by the debris. A dammed river can break through and send a flash flood downstream.
The five kinds of movement are drawn on the types of landslide page, and what PAGASA means by a flash flood is on the flash flood page.
Source: PHIVOLCS, Earthquake Hazards. Read 23 October 2026.
Liquefaction
Liquefaction is ground behaving like a liquid while it shakes. PHIVOLCS places it on lowlands near water: beaches, deltas, riverbanks, reclaimed land and floodplains. For it to happen, the sediment there has to be all four of these things:
- Recently deposited
- Loosely packed
- Water-saturated
- Sandy
What PHIVOLCS says it does:
- Sand and water burst up through vents in the ground, the features known as sand boils.
- The ground sinks, swells, ripples or splits into fissures.
- Rows of parallel fissures open and spread toward the nearby water. PHIVOLCS calls these lateral spreads.
- Poorly built structures sink or tilt.
- Buried structures that can float, such as water pipes, septic tanks and fuel storage, rise up.
Source: PHIVOLCS, Earthquake Hazards. Read 23 October 2026.
Tsunami
A tsunami is a series of waves. PHIVOLCS lists its causes as undersea earthquakes, submarine landslides, meteor impacts and volcanic eruptions, and sorts the ones that can reach the Philippines into two kinds.
- Local tsunamis start within the Philippine region, typically within a hundred kilometers: offshore active faults, the subduction zones around the country, submarine landslides and pyroclastic flows. They can reach the shoreline within 2 to 5 minutes, and every coastal area in the Philippines can be hit by one.
- Far-field tsunamis start elsewhere around the Pacific Ocean or in the Celebes Sea. They can travel from 1 to 24 hours before reaching the coast of the Philippines.
The waves can keep coming for hours and reach far inland. PHIVOLCS says they move houses, buildings and bridges, carry vehicles and debris weighing several tons inland, and that the currents and debris injure and kill people caught in the waves coming in and going out. Seawater can get into freshwater supplies and make them unfit to drink, and the salt can leave farmland unusable for years. The example on the PHIVOLCS page is the 1976 Moro Gulf earthquake.
The three natural signs that a tsunami may be coming, and what each PHIVOLCS bulletin asks you to do, are on the tsunami page.
Source: PHIVOLCS, Earthquake Hazards. Read 23 October 2026.
Coastal uplift and subsidence
The coast can move up or down when the crust moves along a fault or subduction zone. It can happen suddenly during an earthquake, or gradually as the crust slowly deforms between earthquakes. Uplift can widen the coast, move the high tide line out to sea and leave coral reefs and sea life exposed. Subsidence can narrow the coast, move the high tide line inland and drown mangroves.
PHIVOLCS's example is Loon, Bohol, after the 2013 earthquake: the coast rose by 1.5 to 2.2 meters and the beach widened by as much as 300 meters. The edge of the mangroves marks where the coastline used to be.
Source: PHIVOLCS, Earthquake Hazards. Read 23 October 2026.
Which of the six reach your address
PHIVOLCS's HazardHunterPH, whose FAQ says its reports are free, runs an assessment for a point on the map. For earthquakes it covers ground rupture, ground shaking, liquefaction, earthquake-induced landslides and tsunami, with an explanation and recommendations from the agency.
Source: PHIVOLCS, Press release: Hazard Hunting Made Easier with HazardHunterPH Mobile. Read 23 October 2026.
Source: GeoRiskPH, DOST-PHIVOLCS, HazardHunterPH Frequently Asked Questions. Read 23 October 2026.
What to do about them
The hazards are what the ground does. The guides below are what PHIVOLCS asks a household to do.
The earthquake guide During and after a lindol Tsunami signs and warnings