POSSIBLE CAUSE-EFFECT RELATIONSHIPS BETWEEN TWO MEGAHURRICANES (IRMA & MARIA) AND TWO MEGAEARTHQUAKES (CHIAPAS, M 8.1; & MEXICO D.F., M 7.1) IN THE CARIBBEAN REALM (SEPTEMBER 2017)

 

Miguel Doblas1, Eugenio Degroote2, Fernando Anaya3 and Julia De Las Doblas4
1Institute of Geosciences, CSIC-UCM (Spanish Research Council and Complutense University), Ciudad Universitaria, 28006 Madrid, Spain. Email: doblas@mncn.csic.es. 2Higher Technical School of Industrial Engineers, Politechnical University, Madrid,  20006 Madrid, Spain.3Jesus Nazareno Institute, Getafe, 28901 Madrid, Spain. 4Hoyo de Manzanares Town Hall, 28240 Madrid, Spain.


In this paper we suggest that several apparently unconnected meteorological-planetary-seismic natural phenomena coinciding in space/time in the Caribbean/North-American realm in September 2017 might bear causes (1+2) → effect (3) relationships: 1) Meteorological: Unusually repetitive and extreme meteorological “waves” of west-directed Atlantic-derived very strong hurricanes devastating the  Caribbean islands, the Gulf of Mexico and southeastern United States (Harvey, Irma, Katia, María); 2) Planetary: A crustal-pulling full moon tidal phase imposing additional stresses on the gravitationally unstable western Caribbean active margin; and, 3) Seismical: Two major megaearthquakes striking the vicinity of the northwestern Caribbean plate (Chiapas, 09-07-2017, M 8.1; Mexico D.F., 09-19, M 7.1).

In fact, on September 19 (morning, UTC time), we predicted the imminence of a strong earthquake that might strike a sector to the northwest of the Caribbean plate (between Mexico and Honduras), coincident with the arrival of the powerful hurricane Maria that swept the lesser Antilles in the eastern Caribbean.  We were right as this same day (afternoon, UTC time) an earthquake of magnitude 7.1 devastated Mexico DF. (http://ds.iris.edu/message-center/thread/3705/; https://www.laestrella.com.pa/cafe-estrella/planeta/170925/mexico-huracanes-terremotos-relacionados; https://nepabuleici.wordpress.com/2017/09/25/cientificos-espanoles-logran-predecir-el-terremoto-de-mejico/). This prediction was based on our previous observations that suggested a cause-effect relationship between Hurricane Irma in the northern Caribbean (the most powerful in history; 6 to 8 of September) and the 8th of September megaearthquake of Chiapas (M 8.1).

The Chiapas and Mexico earthquakes were anomalous as they occurred along NO-SE normal faults within the Cocos plate: usually they happen along deep reverse faults at the boundary between two plates. In addition, the Chiapas earthquake originated within the Tehuantepec aseismic-gap of the Cocos subduction margin that has remained quiet during the past 100 years (Wade, 2017, Science , September 11).

This hypothesis suggests that the August-September 2017 record-surge of powerful hurricanes contributed to weaken the unstable boundary of the Caribbean plate along its fault-contact with the North American plate to the northeast/east (Harvey, Irma, Jose, Maria) and to the west (Katia), and consequently, the Cocos active margin (subducting towards the east) released part of the accumulated energy through the Chiapas and Mexico earthquakes. The hurricanes-induced heavy rains, violent circular motions and surface underpressures might not be the direct causes of the earthquake but the final trigger. Tectonic forces along the North American-Caribbean plate boundary build up stresses, which are released abruptly as earthquakes (the seismogenic fault simply reaches a threshold). The striking of waves of very wet and powerful hurricanes may give a hint that a quake-prone region is at higher risk of rupturing sooner than expected.

The energy of an average hurricane (category II-III) is equivalent to 200 times the world's electricity production (or 10,000 atomic bombs). This formidable energy multiplies considerably in the case of category V megahurricanes such as Irma (as large as the Iberian Peninsula) that advances very slowly towards the west (while rotating counterclockwise at speeds exceeding 300 km/h), closely following the track of the WE/sinistral seismogenic transform fault zone separating the Caribbean and North American plates that is literally swept by this powerful meteorological vortex/aspirator. The passage of this hurricane generates the following disturbances: intense torsion stresses and strains with the same sense of movement than the transform fault zone bounding the two plates; powerful vertical suction effects produced by the low atmospheric pressures prevailing within the eye of this vortex (where it induces an important elevation of the sea level); and, continuous and massive water-flooding enhancing  the hydroseismic-related microseismicity and such processes as deforestation, soil erosion and crustal unloading; etc.

Two additional factors could represent "the drop filling the glass" in the triggering of the Chiapas earthquake: 1) hurricane Katia was fully active in the southwestern Gulf of Mexico, contributing to destabilize the southern edge of the North American plate; and, (2) a full moon phase prevailing in Mexico during the night of the earthquake that might have exerted a powerful gravitational pulling-effect on the crust, inducing additional stresses on a seismogenic fault and facilitating this huge earthquake: Ide et al., 2016, Nature Geosciences, 9, 834-837) have described this lunar effect during the megaseisms/tsunamis of Sumatra (7.1; 2014), Maule (8.8; 2010) and Tohoku-Oki (8.9; 2011).

 We will undertake a mathematical modelization of the Caribbean plate as an idealized “parallelepiped tile" (bounded by east-/west-dipping subduction zones, to the west and east, respectively) and EW-oriented strike-slip transform faults (to the N and S), in order to calculate the stress/strain pattern governing this lithospheric realm. The westernmost tip of this plate (in the triple union with the Cocos and the North American plates) might have reacted by liberating some of its lithospheric energy through the huge Mexican 8.1 earthquake (just as a "tile" would do). The physical study of the tensional variations occurring in an idealized virtual plate (representing the Caribbean plate) will be made by successive mathematical approximations. On the first place, we will analyze the behavior of an idealized two-dimensional rectangular plate subjected to a stress gradient along its surface, with an estimated tensional distribution similar to a hurricane running through one of its borders. For this purpose we will use different numerical methods in linear approximation by different iterative and descent methods, such as Gauss-Seidel, Jacobi, relaxation (e.g. the preconditioned gradient method). The evaluation of the best method to be used has yet to be determined. This simplified model will allow us to obtain the distribution of superficial stresses, the deformations affecting the idealized rectangular plate and their influence on the triggering of seismic disturbances. Secondly, we will introduce a third independent variable in order to evaluate the vertical suction effect of a hurricane, which will allow us to qualitatively determine the probability of occurrence of seismic disturbances along the plate. We will also quantify the strong left-lateral horizontal torsion scrubbing forces exerted on the surface of the plate by a powerfully spinning hurricane. Finally, we will apply a mixed mathematical model combining both analyses in order to obtain a qualitative/quantitative approximation to the hurricane/earthquake coupling model presented in this paper.


The hypothesis that extreme weather conditions, including hurricanes, have an influence on macroseismicity has already been advanced by some authors (http://www.smithsonianmag.com/science-nature/hurricane-sandy-generated-seismic-shaking-as-far-away-as-seattle-25993081/ ;https://www.xataka.com/ecologia-y-naturaleza/tormentamotos-acabamos-descubrir-nuevo-fenomeno-sismico-que-furia-grandes-tormentas-provoca-terremotoshttp://www.smithsonianmag.com/smart-news/hurricanes-may-cause-earthquakes-38447485/). Although this theory remains an anathema to classical seismology, the existence of "Climatic Earthquakes" has been demonstrated (McGuire, 2013, Oxford, 320 pp). The theory of hydroseismicity (Costain et al., 1987, Seism. Res. Lett., 58, 41-64) suggests that the hydrological variations of the crust may induce earthquakes. The intense erosion caused by catastrophic meteorological phenomena or the melting of polar ice caps releases the crust from a considerable weight, generates earthquakes (Haiti, 2010, Wdowinski and others, 2010, AGU Annual Fall Meeting) and can even influence the movement of tectonic plates (Laffaldano et al., 2011, Earth Planet, Sci. Lett., 104, 503-510). However, as mentioned before, the majority of traditional geophysicists are reticent to accept the new paradigm that “a changing climate can trigger earthquakes, tsunamis and volcanoes” as they have been trained to believe the “tunnel-vision” that the solid lithosphere cannot be altered in any way by such an “ethereal” element as the atmosphere. In this way, it comes as no surprise that many scientists disagree with the possibility that megahurricanes might induce megaseisms: ej., https://www.inverse.com/article/36268-earthquake-mexico-hurricane-irma; https://www.bustle.com/p/did-hurricane-irma-cause-the-mexico-earthquake-it-all-comes-down-to-the-ring-of-fire-2302911.





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