EarthquakeEngineering DisasterRisk VenezuelaEarthquake PhilippinesEarthquake Liquefaction landslides

Landslide and liquefaction mapping becomes critical after major quakes

*Liquefaction hazard mapping for Venezuela highlights zones where saturated ground may have lost strength during shaking. Source: Eos (image by USGS)*

Recent major earthquakes in Venezuela and the southern Philippines have highlighted an important lesson in disaster response: the most serious impacts are not always visible in the first images of collapsed buildings. Landslides, liquefaction and damaged ground can affect communities, block access routes and delay rescue operations long after the initial shaking has stopped.

In Venezuela, the 24 June 2026 double earthquake sequence, with reported magnitudes of 7.2 and 7.5, created severe concern around Caracas and the epicentral region west of the capital. Initial USGS PAGER assessments indicated potential population exposure to earthquake-triggered landslides in the range of 1,000 to 10,000 people. The estimated exposure to liquefaction was higher, reaching the range of 10,000 to 100,000 people.

USGS PAGER landslide hazard map for the Venezuela earthquake sequence, indicating areas where strong shaking may have triggered slope failures. Source: Eos (image by USGS)

Earlier in June, the magnitude 7.8 earthquake offshore Mindanao in the Philippines produced similar concerns. Initial PAGER mapping showed significant landslide hazard and a broad zone of liquefaction potential. In both events, the maps served as an early indication that earthquake impacts could extend beyond the most visible urban damage.

USGS PAGER landslide and liquefaction maps are not final field assessments. They are rapid, first-order estimates based on earthquake magnitude, shaking intensity, terrain, ground conditions and population exposure. However, they can be useful in the first hours after a disaster because they help emergency teams identify where secondary ground failures may have occurred.

Landslides can be triggered when strong shaking destabilises steep slopes, weathered rock, saturated soils or previously weakened ground. They can bury settlements, damage roads, isolate rural communities and prevent rescue teams from reaching affected areas.

Liquefaction occurs when saturated loose soils lose strength during earthquake shaking. The ground may settle, spread laterally or temporarily behave like a fluid. This can damage foundations, tilt buildings, rupture utilities, affect ports and undermine transport infrastructure.

These hazards are often underreported at the beginning of a disaster. Media coverage usually focuses first on major cities, airports, hospitals and collapsed buildings. Remote areas closer to the strongest shaking may remain silent because roads, power and communications have failed. In earthquake disasters, limited information from rural zones can be a warning sign rather than evidence of safety.

The Venezuela and Mindanao events show why post-earthquake response should include geotechnical assessment as well as structural inspection. Buildings must be checked, but so must slopes, river valleys, coastal zones, road cuts, bridges, embankments, ports and areas underlain by soft saturated soils.

In Venezuela, the double sequence may have increased the risk because the first earthquake could have weakened buildings, slopes and ground before the stronger shaking and aftershocks followed. In Mindanao, an additional concern was the possibility of heavy rainfall during the typhoon season, which could worsen earthquake-triggered slope instability.

USGS PAGER maps for the Mindanao earthquake also indicated significant landslide and liquefaction exposure, especially in remote and vulnerable areas. Source: Eos (image by USGS)

After major earthquakes, hazard maps can help guide where to send reconnaissance teams, where to inspect transport corridors, and where isolated communities may need urgent support. Collapsed buildings show the immediate disaster. Landslide and liquefaction maps can help reveal hazards that are less visible in the first hours of response.

Sources: eos.org, eos.org/thelandslideblog, earthquake.usgs.gov