Some fault systems in the world are well known for their destructive potential. Examples are Turkey’s North Anatolian fault and California’s San Andreas. In both cases, large events in the not-too-distant future are widely predicted. In Turkey, the march of magnitude-7 earthquakes towards Istanbul has drawn attention. The fault is both locked and stressed close to the city. For the San Andreas, the southern segment has been quiet for a bit too long to feel entirely safe. In both cases is the particular segment not so easy to see. In Turkey, it lies under water. In California, the fault is not so obvious because of erosion and in sone cases, building activity. But nonetheless, they are well known and relatively well studies, albeit also taken a bit for granted by the people who would be most affected.

Other faults are less studied and the dangers may be underappreciated. We have seen that with the East Anatolian Fault in Turkey which took the country by surprise. Further south, southern Lebanon is at serious danger from the Dead Sea Fault which has regularly caused major destruction with magnitude-7 events but has been silent for over 800 years. Such faults are typically located in regions which attract less attention from science, have shorter records of instrumental data, may be less accessible and are less frequently active so that there is less local awareness of the dangers. People may have more urgent things to worry about in these regions!

And now one of those lesser-known fault systems has failed in a predictable but unexpected event. Caracas has been badly damaged. VC had drawn attention to this region just a few months ago when we wrote ‘Caracas was destroyed by an M7.5 (est.) in 1812 and was again but less severely damaged by a similar-sized event in 1900. An M7.3 earthquake hit further east in 2018. The last significant earthquake in Caracas was in 1967 (M6.6), long enough in the past that the city should be prepared for a recurrence.’ We had no idea it would happen so soon.

Venezuela

The country could be one of the richest in the world. It has immense natural resources, has all the good harbours on the Caribbean Sea, and lies outside the hurricane belt. Of course, wealth attracts unwanted attention and people in charge may not overlook the opportunity for some personal benefit and if the region is a colony, may have their own interests elsewhere in the world. It has left the country both rich and impoverished.

Geologically, the nation is also a mixture. In the west, the Andes lurk, signs of the Pacific ocean. There are two main mountain chains here, the smaller chain along the Pacific ocean, and the larger spur running towards the northeast called the Cordillera the Mérida. Both are considered part of the Andes. The southern part of Venezuela is one of the ancient pre-cambrian shields of the world, in part a calm land of wide open plains and in part more mountainous with the high table mountains of the tepuis and the Guiana highlands (with the world-famous Angel Falls). The far east is the delta of the Orinoco river. And the north is the border with the Caribbean sea, with coastal mountains (known as the coastal Andes) and earthquakes. There are no active volcanoes in-land, even if one of the peaks in Caracas is called El Picacho de El Volcán. There are some mud volcanoes in the Orinoco delta.

Faults

Given this geology, it is not a surprise that the main active faults are along the Andes and along the Caribbean. This follows rather well the main population centres: this combination is one reason why earthquakes here can be devastating.

The two main plates are the Caribbean plate to the north, and the South American plate. The main faults follow this boundary region. A second fault system follows the edge of the Andes and associated mountain region. The faults are right lateral, meaning a slip-strike where the opposite side from where you are standing is moving to the right. In effect, the Caribbean plate is moving eastward with respect to Venezuela while Colombia is moving northeastward. However, it is of course more complicated. The Caribbean plate is also moving towards Venezuela. There is a crumple zone – the coastal mountains – and some of the plate has accreted onto South America. There is accretionary prism is deformed, mainly off-shore.

The main fault system runs from Trinidad to the west. The remarkably straight line of the northern coast, all the way from northern Trinidad to the line of the coastal Andes is this fault line. Further west it splits in two, one segment continuing to the west and the other following the Cordillera the Mérida towards the southwest. Towards Trinidad, the fault has abandoned its original location and is now bending to the southern edge of Trinidad. There are several other, small fault segments bit these are the main ones.

El Pilar

Let’s first look on the east side, towards Trinidad. There is a sliver of Venezuela between two Gulfs, on the east side almost touching Trinidad. The main city in this region is Cumaná, which lies on the southeast tip of the narrow Golfo de Cariaco. The fault line here has split in two, with the El Pilar fault (VE-13 on the map) the dominant one, and the San Sebastián fault (VE-16) running a bit further north. The two are running either side of the Golfo the Cariaco, a pull-apart basing.

The El Pilar fault is considered the most active and dangerous in Venezuela. Cumaná has been damaged or destroyed by earthquakes eight times, starting in 1530 and ending (so far) in 2018. In 1797 and 1929, the earthquake happened in the Golfo the Cariaco, and in 1530 and 1853 in the sea west of Cumaná. The 1997 earthquake measured magnitude 6.8. The 2018 event occurred further east, at the western tip of the Golfo de Paria, and was deep: in spite of the magnitude 7.3, damage was more limited than usual in this region. The typical rupture length on the El Pilar fault is 30-50 km and over time it seems the earthquakes migrate eastward. Cumaná seems in some ways remarkably similar to Istanbul!

Oca–Ancón and Boconó

On the other side of the country are two main faults. The  Oca–Ancón Fault runs along the north, between the Gulf of Venezuela and the Lago de Maracaibo (VE-01a for the Oca fault, VE-01b for the Ancón fault on the map). This is fairly inactive with recurrence times of 2000 to 4000 years. However, when it fails it can produce magnitude 7.5 events. The Oca fault seems safe at the moment, but the Ancón last ruptured 4500 years ago, so has reached its recurrence time. This sectin of the fault should be considered a risk.

The fault running along the mountains to the southwest is much more active. This is VE-06 on the map and is called the  Boconó Fault. It is a young fault which shows but lateral motion (around 30 km offset) and thrusting. Three major historical earthquakes are attributed to it, in 1610, 1812 and 1894. The 1812 event likely ruptured the entire fault north of the indicated location, based on the damage which included Caracas. It may be an event similar to the 2026 earthquakes.

San Sebastián 

The faults on the east and west are connected by the San Sebastián fault, already mentioned in connection to El Pilar. It runs along the coast north of Caracas. About 50 km west of Caracas, it splits into the Boconó fault an inactive section towards the Oca–Ancón Fault. On the east, the El Pilar fault merges with it.

The San Sebastián fault was considered as relatively inactive. This may be related to the fact that it lies off-shore, and is thus not easy to study or even see. In the USGS overview of tectonics of Venezuela of 2000, the fault is hardly mentioned. That only changed a few years later when the destructive Caracas earthquake of 1900 (magnitude 7.7) was attributed to the San Sebastián. By the way, the fault comes on-shore only in one short section where it follows the runway of the Caracas’ international airport. It is named after the local municipality of San Sebastián de Maiquetía.

Earlier, the 1900 earthquake had been attributed to the Tortuga Fault which runs 20 km further north along the southern coast of Tortuga island where there is a sharp drop in elevation. However, this fault is now known to much shorter than thought and does not extend far beyond the island. An M7.7 requires a rupture length of 200 km or so, which is just about the entire length where the San Sebastián fault is the only active one.

The San Sebastián fault runs along he coast line, along the edge of the coastal mountains and along the edge of a 500-meter deep sea basin. There is over 2 km of elevation difference between the two sides of the fault. It makes sense that this fault is more active than had been realized.

Caracas

The city has a history of significant earthquakes. On 26 Marc 1812, the destruction coincided with Venezuela’s war of independence. Caracas and La Guaira (the port of Caracas) were described as raised to the ground. That may reflect the ancient standard of building. Caracas is located in a fertile but rugged valley with limited room for expansion and few resources: the locals were dependent on subsistence farming. The original buildings were flimsy, made from stone, earth and wattle.

Thde first recorded earthquake was on Saint Barnabas’ Day, 11 June 1641. There was extensive damage, the churches and state buildings were destroyed and 84 people died. Rebuilding took many years. Even the important main fort at the port took 5 years; Caracas itself took several decades before rebuilding started. This may not have been such a large event: given the building quality, a low magnitude-6 has been proposed for it.

On 26 March 1812, a much larger earthquake demolished the city. It changed the land. Rivers changed their course, the city flooded and a lake formed. Over 15,000 people died. There was calls to move the capital afterwards. A magnitude of 7.1-7.7 has been calculated for this earthquake. The reports at the time suggests there were two events, 30 minutes apart, one near Caracas and the other near Merida along the Boconó Fault.

29 October 1900, a similar event hit, with a magnitude around 7.5. In spite of the strength, the damage in Caracas was much more limited than in 1812. Most damage was at the coast. The earthquake may have been located further east along the San Sebastián fault, based on damage much further east.

On 29 July 1967, a smaller earthquake hit about 20 km west of Caracas. The magnitude of this event was 6.6. This caused major damage and around 250 people died.

24 July 2026

Just after 6pm local time, two large earthquake hit in quick succession. In Caracas, they were felt less than a minute apart. The first earthquake was around magnitude 7.1; the second was considerably stronger at magnitude 7.5. There is significant damage in Caracas and La Guaira, with some high rise buildings having collapsed but others seem fine, based on the available photos. There is no information yet on damage in other places.

The epicentres of both events are close together, and located near where the San Sebastián fault and the Boconó fault connect. The first event appears to have broken the northernmost section of the Boconó fault. This area has several towns but is not densely populated. Judging from the USGS shaking map, San Felipe (with a population of 200,000) may be the closest city to be affected. (It is called a ‘small town’ in news reports.)

The second earthquake had an epicentre just to the north, but now the shaking extended eastward. This indicates that now the San Sebastián fault gave way, and broke up to (at least) Caracas. It may have ended at the segment which broke in 1967 although that is speculation. The USGS shaking map seems to show the strongest shaking again near the epicentre, and a little lower a thin region near the coast up to Caracas. The earthquakes were strike-slip faulting. The first earthquake was located at some 20 km depth; the second one was shallower at around 10 km.

What caused the damage in Caracas, which was not located in the area of the highest shaking, judging from the USGS maps. There will have extensive landslides in the mountainous regions. Liquefaction may have occurred where building was on sediments. But the collapse of some high rise buildings may suggest that the main cause was building defects. Each building has its own fundamental frequency, where it responds most strongly to shaking and amplifies it. If this coincides with a frequency present in the earthquake, the building is at risk. The collapsed buildings may not have been strong enough or lacked damping mechanisms in the design.

This would explain the patchy damage in and near Caracas. Whether the situation is worse in towns nearer the epicentre seems not yet known.

Albert, June 2026