Teotihuacan ancient culture depressed by a megaearthquake associated to the seismic Guerrero gap recorded in Cacahumilpa Cave and EAEs (Mexico)

20th Congress of the International Union for Quaternary Research (INQUA). Dublin, 25th and 31st July 2019, AbstractTeotihuacan was one of the more blossom cultures in the Mesoamerica pre-Hispanic times, located in the central part of Mexico. The archaeological remains are one of the most famous tourist places in our days. During his highest splendorous time (Classic Period, ca 600 CE yr.), close to 200.000 people lived in an urban city with monumental buildings. The city was arranged in one main street of 2 km, oriented N15ºE (Avenida de los Muertos), with impressive religious buildings like the Sun Pyramid, one of the greatest pyramid in America, the Moon pyramid at the north and the Feathered Snake Pyramid (the Citadel), at the south part of the city. The city was a dominant center point of the Mesoamerican culture between the years 125 and 650 CE. In the year 650 CE (Epiclassic period), a dramaticdecrease of the urban population was noted by several authors and archaeologists. Finally, the city was totally abandoned sometime before the Aztec culture rose as dominant (c.a. 800 CE). A systematic analysis of the main pyramids shows several Earthquake Archaeological Effects (EAEs) affecting the south staircase of the Sun Pyramid, with reinforcement of the E-W sides and high damage affecting the original south staircase of the Feathered Snake Pyramid. All of these building damages appears to be coeval between the years 600 and 650 CE. Furthermore, a speleoseimic analysis of the Cacahuamilpa cave shows multiple coseismic stalagmite and stalactite oriented collapses, cave located at Tasco city (130 km away from Teotihuacan). Numerical dating of these sismothems suggests that the speleothems collapse and tilting occurred between the year 463±50 and 1064 ±20 yrs. CE, according to diverse authors. To check our proposal, we produced a ShakeMap for an Mw 8.1 to Mw 8.4 earthquake, with a theoretical epicenter located at the Guerrero seismic gap segment of the pacific subduction zone (388 Km from Teotihuacan, N210ºE direction), simulating a rupture between 150 to 292 Km of reverse faulting of this segment of the Middle American Trench (MAT). Calculated seismic ground accelerations for these theoretical events can explain both the cave damage at Tasco and building damage at Teotihuacan (0.32 g; VIII ESI-07). Therefore, we consider the possibility that a strong earthquake (Mw>8) associated to the Guerrero segment could be the responsible for the great population decline and subsequent abandonment of the ancient Teotihuacan. In this way, there is the possibility to link strong seismic activity with outstanding “cultural reliefs” occurred in Mesoamerica. This proposal does not conflict with either of the existing theories for the Teotihuacan abrupt collapse (droughts, revolutions, volcanic eruptions, etc.), because the sudden overlapping of natural disasters would increase famine episodes, internal warfares and community unrests for brief periods of time.Instituto Geológico y Minero de España, EspañaUniversidad Autónoma de Madrid, EspañaEscuela Politécnica Superior, Universidad de Salamanca, EspañaEscuela Técnica Superior de Ingenieros Agrónomos, Universidad Politécnica de Madrid, Españ