Pérou 28 juin 2024  Mw 7.2

Séisme de magnitude Mw entre 7.1 et 7.2 au centre-sud Pérou, 8 km à l'Ouest d'Atiquipa. Le séisme localisé au niveau de la côte, avec un mécanisme au foyer inverse et une profondeur entre 17 et 31 km (Moment Tensor inversions) a les caractéristiques typiques d'un séisme de chevauchement sur le contact interplaque.

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Localisation USGS  https://earthquake.usgs.gov/earthquakes/eventpage/us6000n8tq/executive  :

• 2024-06-28 05:36:37 (UTC)

• 15.811°S 74.445°W

• 28.0 km depth

Localisation EMSC  https://www.emsc-csem.org/Earthquake_information/earthquake.php?id=1676866 :

Date time2024-06-28 05:36:38.3 UTC

Location-15.819 ; -74.364

Depth 30 km

Distance 244 km SE of Ica, Peru / pop: 246,000 / local time: 00:36:38.3 2024-06-28

51 km SE of Acarí, Peru / pop: 4,400 / local time: 00:36:38.3 2024-06-28

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Compilation des mécanismes au foyer publiés rapidement après le séisme (Moment Tensor inversion) sur le site du CSEM (EMSC) https://www.emsc-csem.org/Earthquake_information/earthquake_map.php?id=1676866   :

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Carte préliminaire de distribution des PGA https://twitter.com/Asismet_IF/status/1806605293746352566 :

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Image de la rupture par back-projection. Transmis par Jean-Paul Ampuero, analyse réalisée par Yuqing Xie (Geoazur).

High-frequency back-projection result by Yuqing Xie (Geoazur), using the USA seismic network as teleseismic array, obtained automatically some hours after the event. We only show the first 23 seconds, a duration estimated based on the source time function by Geoscope (back-projection alone does not resolve well the end of the rupture, because weak late sources may interfere with scattered and reflected phases from earlier stronger sources).

The map plot (left) shows the locations of sources of coherent high-frequency radiation (circles) as a function of time every 1 second (color scale) and their uncertainty estimates (light ellipses). Star and beachball are the epicenter and focal mechanism by USGS, respectively.

The space-time plot (right) shows the high-frequency sources as a function of time (in seconds) and of location projected on a line striking 167 degrees (strike based on the thrust plane of USGS focal mechanism). The black line indicates the estimated average rupture speed (apparent speed along the projection line).

This back-projection images a unilateral rupture propagation to the North-West, at subshear average speed (somewhat faster than 1.8 km/s), over a rupture length < 40 km.