Guatemala paleoseismicity: from Late Classic Maya collapse to recent fault creep.

Christian Teyssier,Flavio S Anselmetti,Gilles Brocard

doi:10.1038/srep36976

Abstract

We combine ‘on-fault’ trench observations of slip on the Polochic fault (North America-Caribbean plate boundary) with a 1200 years-long ‘near-fault’ record of seismo-turbidite generation in a lake located within 2 km of the fault. The lake record indicates that, over the past 12 centuries, 10 earthquakes reaching ground-shaking intensities ≥ VI generated seismo-turbidites in the lake. Seismic activity was highly unevenly distributed over time and noticeably includes a cluster of earthquakes spread over a century at the end of the Classic Maya period. This cluster may have contributed to the piecemeal collapse of the Classic Maya civilization in this wet, mountainous southern part of the Maya realm. On-fault observations within 7 km of the lake show that soils formed between 1665 and 1813 CE were displaced by the Polochic fault during a long period of seismic quiescence, from 1450 to 1976 CE. Displacement on the Polochic fault during at least the last 480 years included a component of slip that was aseismic, or associated with very light seismicity (magnitude <5 earthquakes). Seismicity of the plate boundary is therefore either non-cyclic, or dominated by long-period cycles (>1 ky) punctuated by destructive earthquake clusters.

Highlights

The North America-Caribbean plate boundary is a left-lateral, mostly submarine structure that surfaces here and there through the Greater Antilles and Central America
We explore the implications of this record for the seismic behavior of the plate boundary, the demise of the Classic Maya civilization, and the likelihood of future major earthquakes
The spatial spread of reported earthquake-related destructions after the Spanish colonization does not evidence any other major earthquake on the Motagua fault; the reports suggest the possibility of three major earthquakes in 1538, 1785, and 1816 CE on the Polochic fault[5,19]

Summary

Introduction

The North America-Caribbean plate boundary is a left-lateral, mostly submarine structure that surfaces here and there through the Greater Antilles and Central America. In Guatemala, two major structures, the Motagua and Polochic faults (Fig. 1) accommodate under the current interseismic cycle roughly 3/4 and 1/4 of the ~2 cm/y left-lateral motion between the North American and Caribbean plates[17]. It has been stressed that the collective inventory of earthquakes along the Polochic and Motagua faults over the last millennium seems insufficient to accommodate the total left-lateral motion accumulated across the plate boundary over the period, suggesting a deficit of major seismic events[20]. In this study we combine on-fault observations of surface displacements in soils deposited during the past millennium over the Polochic fault trace at Agua Blanca, with a nearby record of lacustrine seismites that spans the past twelve centuries in lake Chichój (Fig. 2)

Methods

Results

Conclusion