By David Jacobson, M.Sc., Temblor
A large earthquake causes damage but no fatalities
Yesterday, at just past 9:30 p.m. local time, a M=7.3 earthquake struck the northeastern coast of Venezuela. Fortunately, this quake occurred in a relatively remote area, and there are no reported deaths as of this morning. However, there is damage from the quake, including in Caracas, Venezuela’s capital, nearly 600 km (370 mi) away. Even though only light shaking was recorded in Caracas, according to the USGS ShakeMap, it was great enough to cause the top ten floors of an abandoned skyscraper to shift and lean precariously over the road far below. According to CNN, that area has been evacuated. Closer to the epicenter, in places such as Port of Spain, Trinidad and Tobago, additional structural damage has been observed in buildings.
A region marked by strike-slip activity
While seismic activity is not uncommon in this region, yesterday’s M=7.3 quake is much deeper, and had different motion than the majority of quakes that impact Venezuela. Northern Venezuela is marked by the boundary between the South American and Caribbean plates. In this location, plate motion is approximately 20 mm/yr, and typically results in right-lateral strike-slip earthquakes at shallow depths. However, yesterday’s earthquake was compressional in nature, and occurred at a depth of 123 km. Therefore, it did not occur on the plate boundary, but rather well beneath it.
Even though much of the seismicity in the region is dominated by the strike-slip plate boundary, the region is also subject to compression and some believe that off the northeastern coast of Venezuela there is an ancient, or not fully-formed subduction zone (Pindell et al., 2015). This zone, which Pindell et al. term the Proto-Caribbean Inversion Zone has the same rough orientation as the strike of yesterday’s earthquake. So, it at least seems possible that the event occurred on this structure, which could pose additional hazards for Venezuela and the southeastern Caribbean.
Regardless of what structure yesterday’s earthquake occurred on, what this event highlights is the seismic hazard of the region. This illustrates both that large earthquakes are possible, and that even weak to light shaking can cause significant damage to buildings not of the highest build quality, as was seen in Caracas. Therefore, it is not only important to know the seismic hazard of where you live, but whether or not your home or office is capable of withstanding shaking.
Jame L. Pindell, Lorcan Kennan, David Wright & Johan Erikson, Clastic domains of sandstones in central/eastern Venezuela, Trinidad, and Barbados: heavy mineral and tectonic constraints on provenance and palaeogeography, From James, K. H., Lorente, M. A. & Pindell, J. L. (eds) The Origin and Evolution of the Caribbean Plate. Geological Society, London, Special Publications, 328, 743–797