A day later, it is not yet fully understood whether this was two faults, two ruptures on the same fault in different sections or in the same section. Nevertheless, there are a couple of valuable takeaways that are emerging (CBC image).

1. The first one is that if this is two faults, and this has happened before in 1925 in the same area, that suggest this mode of multiple fault rupture might be more common that we commonly think. This sort of mode was rarely considered before the 2016 Kaikoura earthquake (Howarth et al., 2021), and now is appearing more common. The recent discovery that Cascadia and the Northern San Andreas commonly rupture in closely spaced pairs is another example (Goldfinger et al., 2025). This means that consideration of multi-fault rupture should be taken more seriously where these events may occur in populated areas. For much of the world, this is not presently the case. If this mode is more common, it could be much more common in the case where faults may be partially synchronized, resulting in a common mode of multiple ruptures. Considering this possibility would increase the hazard level at a given setting, and building codes would need to be beefed up to cover that.
2. The second observation that many will consider unlikely, is triggering of more distant earthquakes. Most would say for example, that the Japanese M6.9 earthquake 25 minutes later was unrelated. This is because the dynamic triggering threshold is considered to be high enough that such a distant event could not exceed it. But as it turns out, the S-wave travel time from the Venezuela events is about 23.5 minutes. Better seismologists than I will refine this number, and perhaps this relationship will go away. If not, then it’s intriguing to say the least. This type of remote triggering at such large ranges is normally dismissed, however in two papers, O’Malley et. al. (2018) show that if you comb through the global earthquake catalogs, and allow a three-day window of observation, there is a sharp jump in earthquake frequency following M5 or larger events. So remotely triggered events may not occur exactly on arrival of the remote waves, btu may have their stress increase just very slightly, and for faults that are already very, very close to rupture, a very small perturbation may trigger them. There is a viable hypothesis that fault-gouge pore-pressure dynamics may be the mechanism (Huang et al., 2026).
3. The third takeaway is the obvious vulnerability of Caracas and many other cities around the world. This of course is not new, but affects virtually all cities with the possible exception of those in highly resilient Japan. As retrofitting entire cities if a very difficult, time-consuming and expensive proposition that is not underway in serious fashion anywhere in the world, what do we do in the short-term? Unfortunately, this is a very tough situation. With the high numbers of collapse hazard buildings, people who live and work on upper floors will fare very poorly in all likelihood. How helpful is it to tell people that “drop, cover and hold on” is the only possible earthquake response? When we do that, it’s a palliative measure that makes people feel there is an effective response in this situation. This in turn makes it less likely to push for retrofits, consider another workplace or home, or take other defensive measures ahead of time. In such situations, people in lower floors of older buildings are advised to escape in Mexico and Israel, the only countries that have carefully thought through this exact problem (Goldfinger et al., 2022) In Oregon, this type of split policy is encouraged for schools as a matter of State Law, the only part of the US that does so. Peer reviewed studies have shown that a “situational awareness” policy is more effective that a single on size fits all recommendation in many settings (GeoHaz International, 2018).

References

Howarth, J. D., Orpin, A. R., Kaneko, Y., Strachan, L. J., Nodder, S. D., Mountjoy, J. J., Barnes, P. M., Bostock, H. C., Holden, C., Jones, K., and Cağatay, M. N., 2021, Calibrating the marine turbidite palaeoseismometer using the 2016 Kaikōura earthquake: Nature Geoscience, v. 14, no. 3, p. 161-167.

GeoHazards International, 2018, Developing Messages for Protective Actions to Take During Earthquake Shaking, GeoHazards International, Menlo park, CA, USA, 79 p.

Goldfinger, G., 2022, Opinion: When the next Cascadia megaquake strikes, here’s what I’ll do, Temblor, http://doi.org/10.32858/temblor.242

Goldfinger, C., Beeson, J., Black, B., Vizcaino, A., Nelson, C. H., Morey, A., Patton, J. R., Gutiérrez-Pastor, J., Romsos, C., and Walzcak, M. D., 2025, Unravelling the dance of earthquakes: Evidence of partial synchronization of the northern San Andreas fault and Cascadia megathrust: Geosphere, v. 21, no. 6, p. 1132-1180.

Huang, C., and Yang, J., What triggers seismicity thousands of kilometers away from a mainshock?: Science Advances, v. 12, no. 26, p. eaec4754.

O’Malley, R. T., Mondal, D., Goldfinger, C., and Behrenfeld, M. J., 2018, Evidence of Systematic Triggering at Teleseismic Distances Following Large Earthquakes: Scientific Reports, v. 8, no. 1, p. 11611.