EVIDENCE OF EARTHQUAKES BURIED AT THE MAYAN SITE OF QUIRIGUA IN GUATEMALA: AN EVALUATION OF ARCHAEOLOGICAL EXCAVATION ARCHIVES

The Mayan archaeological site of Quirigua is located on alluvium of the lower Motagua River Valley near the epicenter of the 1976 M7.5 Guatemalan earthquake that ruptured the North American-Caribbean plate boundary along the Motagua fault. Previous publications have posited that an 830 CE earthquake is documented at the site. The purpose of this study is to review the archaeoseismic evidence of past earthquakes at the Quirigua site and to better constrain the date of the event(s). We examined the archival materials from the excavations of Quirigua that are housed at the Penn Museum (University of Pennsylvania) and Peabody Museum (Harvard University). These data include the excavation field notes of Sylvanus Morley (1911-1934) and original notes, plans, sections, photos, and artifact analyses of the team led by Robert Sharer (1974-1979). The Terminal Classic construction phase at Quirigua began at 810 CE with a dated sculpted frieze, the addition of buildings and steps to the acropolis, and marble facings on structures. This occupation phase likely lasted into the mid-ninth century, although a precise termination age is unknown. The Morley and Sharer excavation descriptions indicate that the latest phase of occupation at Quirigua include human skeletal remains and in situ smashed ceramics on living surfaces below collapse horizons which is interpreted as evidence for an earthquake. The collapsed structures include final phase adobe construction and repurposed acropolis buildings. The metal, Plumbate pottery, and carved stone chacmool artifacts recovered from the upper stratigraphic level suggest a post-Classic date of the earthquake. The earthquake causing the final demise of the settlement likely occurred in the late 9^th century. As historical earthquake catalogues in Central American only extend to the Spanish era starting in the 16^th century, it is important to critically evaluate evidence and timing of the paleoearthquake records such as the one at the archaeological site of Quirigua.