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Abstract
Recent studies have shown that the Nicoya Peninsula of northwestern Costa Rica is moving northwestward ~11 mm a−1 as part of a tectonic sliver. Toward the northwest in El Salvador the northern sliver boundary is marked by a dextral strike-slip fault system active since Late Pleistocene time. To the southeast there is no consensus on what constitutes the northern boundary of the sliver, although a system of active crustal faults has been described in central Costa Rica. Here we propose that the Haciendas-Chiripa fault system serves as the northeastern boundary for the sliver and that the sliver includes most of the Guanacaste volcanic arc, herein the Guanacaste Volcanic Arc Sliver. In this paper we provide constraints on the geometry and kinematics of the boundary of the Guanacaste Volcanic Arc Sliver that are timely and essential to any models aimed at resolving the driving mechanism for sliver motion. Our results are also critical for assessing geological hazards in northwestern Costa Rica.
Highlights
Recent studies have shown that the Nicoya Peninsula of northwestern Costa Rica is moving northwestward ~11 mm a−1 as part of a tectonic sliver
By documenting the geometry and kinematics of this fault system on the margin of the Guanacaste Volcanic Arc Sliver (GVAS) we provide constraints that are essential for models of sliver motion that aim to disentangle the relative contributions of ridge collision[5, 10], oblique subduction[2] or trailing edge plate forces[14]
Central Costa Rica occupies the southern boundary of the Caribbean plate (CA) where it is in contact with the Panama microplate, and is bounded to the southwest by the Middle America Trench (MAT, Fig. 1)
Summary
Recent studies have shown that the Nicoya Peninsula of northwestern Costa Rica is moving northwestward ~11 mm a−1 as part of a tectonic sliver. We document a fault system that we suggest serves as the northeastern margin of the sliver, and that traverses the Guanacaste volcanic arc The configuration of this tectonic boundary, referred to as the Haciendas-Chiripa fault system, requires that what has previously been described as a forearc sliver[10] includes most of the Guanacaste volcanic arc. By documenting the geometry and kinematics of this fault system on the margin of the Guanacaste Volcanic Arc Sliver (GVAS) we provide constraints that are essential for models of sliver motion that aim to disentangle the relative contributions of ridge collision[5, 10], oblique subduction[2] or trailing edge plate forces[14]. Northwestern Costa Rica is dominated by the northwest-trending, extinct (~1.0–2.2 Ma) Monteverde volcanic arc, and the active Guanacaste volcanic arc (Fig. 1a) reflecting subduction of the Cocos plate[19]. This influence ceases toward the northwest at approximately the Gulf of Nicoya[21], with the exception of the southernmost tip of the Nicoya Peninsula where the incoming Fisher Seamount Chain drives high Holocene uplift rates (~6 m ka−1) and northward tilting[22]
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