iJournals: International Journal of Social Relevance &Concern (IJSRC) ISSN-2347-9698 Volume 10 Issue 1 January 2022 Valentino Straser; Daniele Cataldi; Gabriele Cataldi, Volume 10 Issue 1, pp 41-57, January 2022 Pre-seismic phenomena that preceded the M7.0 earthquake recorded in Acapulco (Mexico) on September 8, 2021 Authors: Valentino Straser 1 ; Daniele Cataldi 2-3 ; Gabriele Cataldi 2 1 - Department of Science and Environment UPKL Brussel (B);2 -PermanentFoundationG. Giuliani - Onlus (I); 3 - Radio Emissions Project (I). E-mail: valentino.straser@gmail.com 1 ;daniele77c@gmail.com 2-3 DOI: 10.26821/IJSRC.10.1.2022.100107 ABSTRACT This study analyzes the strong earthquake, magnitude 7, that occurred near Acapulco, Mexico, on September 8, 2021. The earthquake, originating at a depth of about 20 km, waspreceded by a series of electromagnetic phenomena, detected by the Radio Emissions Project station in Rome and the international Radio DirectionFinding network. The electromagneticsignals were compared with the data collection, recordedsince 2008, and fallinto the typology of pre-seismic signals of potentially destructive earthquakes. The study is proposed both to add new data for the understanding of the mechanism of earthquakes and a crustal diagnosis and, in perspective, for a pre-earthquake alert function. Keywords: Seismic Precursors, Mexico, Solar Activity, Spaceweater, Radio-anomaly. 1 – INTRODUCTION Since 2008, researchers from the Radio Emissions Project have highlighted a series of electromagnetic signals that always seem to precede strong earth- quakes, these studies were presented for the first time in 2013 [1] thanks to the use of the NASA INSPIRE VLF-3 radio receiver. Later, the group of researchers were able to build a series of radio receivers capable of detecting the Earth's geomagnetic variations that were able to detect the electromagnetic variations that seemed to precede the strong earthquakes [2] [3]. In 2014, these studies were able to observe a clear corre- lation between solar activity and the occurrence of earthquakes. The evidence was observed on the "near Earth" solar wind proton density variation [4]. The dis- coveries that took place in 2014 were able to provide greater information for understanding Earth's seismo- genesis, in relation to solar activity, in which the group of researchers then continued to perform studies to un- derstand its mechanisms [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18]. In 2017, researchers from the Radio Emissions Project started using an electromagnetic detection system based on RDF - Ra- dio Direction Finding technology [19]. The studies car- ried out with this new technology, used for the first time in the field of research of geomagnetic seismic precursors, provided further important information on the mechanisms that seem to precede earthquakes, and in general provided azimuth indications capable of highlighting, through triangulation of the electromag- netic signals, the geographical area where an earth- quake will then occur [19] [20] [21] [22] [23] [24] [25] [26] [27] [28] [29] [30] [31] [32] [33] [34]. The studies carried out with the RDF methodology have allowed us to understand that there are electromagnetic signals located at the hypocentral level, where energy from tectonic stress is concentrating, in the fault surface [35] [36] [37]. These studies were supported by working hypotheses put forward by the group of researchers starting from 2009. In this case, the methodology used by the Radio Emis- sions Project exploits the study of solar activity and the precursors identified already in 2012 (Solar Seismic Precursors or SSPs; Interplanetary Seismic Precursors or ISPs; Seismic Geomagnetic Precursors or SGPs), following a long work of electromagnetic environmen-