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Open AccessArticle

Natural Time Analysis of Seismicity within the Mexican Flat Slab before the M7.1 Earthquake on 19 September 2017

1
Instituto de Geofísica, Universidad Nacional Autónoma de México, Circuito Institutos S/N, C.U., C.P. 04510 México City, Mexico
2
Departamento de Ciencias Básicas, Universidad Autónoma Metropolitana, C.P. 14387 México City, Mexico
3
Departamento de Física, Escuela Superior de Física y Matemáticas, Instituto Politécnico Nacional, UP Zacatenco, C.P. 07738 México City, Mexico
4
Department of Physics, Solid Earth Physics Institute, National and Kapodistrian University of Athens, Panepistimiopolis, 157 84 Zografos, Greece
5
Section of Condensed Matter Physics, Department of Physics, National and Kapodistrian University of Athens, Panepistimiopolis, 157 84 Zografos, Greece
*
Author to whom correspondence should be addressed.
Entropy 2020, 22(7), 730; https://doi.org/10.3390/e22070730
Received: 8 May 2020 / Revised: 15 June 2020 / Accepted: 28 June 2020 / Published: 30 June 2020
One of the most important subduction zones in the world is located in the Mexican Pacific Coast, where the Cocos plate inserts beneath the North American plate. One part of it is located in the Mexican Pacific Coast, where the Cocos plate inserts beneath the North American plate with different dip angles, showing important seismicity. Under the central Mexican area, such a dip angle becomes practically horizontal and such an area is known as flat slab. An earthquake of magnitude M7.1 occurred on 19 September 2017, the epicenter of which was located in this flat slab. It caused important human and material losses of urban communities including a large area of Mexico City. The seismicity recorded in the flat slab region is analyzed here in natural time from 1995 until the occurrence of this M7.1 earthquake in 2017 by studying the entropy change under time reversal and the variability β of the order parameter of seismicity as well as characterize the risk of an impending earthquake by applying the nowcasting method. The entropy change ΔS under time reversal minimizes on 21 June 2017 that is almost one week after the observation of such a minimum in the Chiapas region where a magnitude M8.2 earthquake took place on 7 September 2017 being Mexico’s largest quake in more than a century. A minimum of β was also observed during the period February–March 2017. Moreover, we show that, after the minimum of ΔS, the order parameter of seismicity starts diminishing, thus approaching gradually the critical value 0.070 around the end of August and the beginning of September 2017, which signals that a strong earthquake is anticipated shortly in the flat slab. View Full-Text
Keywords: seismicity; natural time analysis; entropy; variability; nowcasting; plate tectonics seismicity; natural time analysis; entropy; variability; nowcasting; plate tectonics
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Flores-Márquez, E.L.; Ramírez-Rojas, A.; Perez-Oregon, J.; Sarlis, N.V.; Skordas, E.S.; Varotsos, P.A. Natural Time Analysis of Seismicity within the Mexican Flat Slab before the M7.1 Earthquake on 19 September 2017. Entropy 2020, 22, 730.

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