Severe magnitude earthquake (Mwpd) 7.6 (estimated by the Tsunami-INGV Alert Centre - 7.4 estimated by USGS) originated yesterday 23.06. 2020 at 17:29 Italian time (10:29 local time) in the State of Oaxaca, South West Mexico, between the Cocos plate and the North American plate, triggered a tsunami alert (Watch) by the Pacific Tsunami Warning Center (PTWC) for Mexico, Guatemala, Honduras and El Salvador.
Data collected by local mareographers (fig.1 - Salina Cruz), show the changes due to the tsunami starting at 16:15 UTC. The tsunami is a complex event, the first wave is not always the highest and most dangerous and, once generated, it can last for many hours before the situation returns to its initial state of calm. In fact, it must be remembered that tsunami waves transmit a large amount of energy along the entire water column, from the bottom of the sea to the surface.
Fig. 1 Mareografo - Salina Cruz
The effects of the severe earthquake, felt yesterday in a large area, are visible in the videos below and in others on the web.
The amateur videos filmed during the earthquake shake, are useful to remember what are the signs that may precede a tsunami and how to behave accordingly:
- Being near the sea and feeling the earth shake;
- see a long, compact wave on the approaching horizon;
- to receive news of a strong earthquake near the coast;
- watching the water level rise rapidly;
- watch the water level drop rapidly;
- hear a deep and rising noise coming from the sea (like a train or a low-altitude plane).
In all these cases, move as high and as far away from the coast as possible without waiting for a tsunami alert to be issued. In any case, it should be remembered that beaches are NOT a safe place in case of an earthquake near the coast.
The Italian municipalities have developed their own Emergency Plans (PEC) which, in addition to being public and available on the web, are a useful tool for knowledge and risk mitigation. Inform yourself about the dangers of your territory and how to behave in case of emergency.