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Abstract Trench‐parallel translation of the Central American Forearc (CAFA) is the result of strain partitioning along the Cocos and Caribbean (CA) convergent margin. Unlike the tectonics of northwestern Costa Rica and El Salvador, CAFA‐CA relative motion in Nicaragua is not accommodated on margin‐parallel fault systems. Rather, the northwest‐trending dextral shear is accommodated on margin‐normal sinistral strike‐slip faults that approximate the motion of a margin‐parallel fault (i.e., bookshelf faulting). We compare a new Global Positioning System interseismic horizontal velocity field to analytical and numerical models to show that the bookshelf faulting model can produce the observed velocity field and provide insight into the kinematics and configuration of the margin‐normal fault system. We find that a fault system with 20 km‐long parallel to sub‐parallel margin‐normal sinistral faults, spaced ∼5 km apart, locked from the surface to 5 km depth, and with interseismic slip deficits of 4 mm yr−1, can replicate the observed velocity field. These findings have implications for the region's seismic hazard where shallow moderate‐magnitude earthquakes will have reoccurrence intervals of ∼50 years. These findings are also important for volcanic hazard estimation and unrest forecasting because the margin‐normal faults are in the volcanic arc and magma‐tectonic interactions have been documented along the CAFA.
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Cascading Hazards in a Migrating Forearc‐Arc System: Earthquake and Eruption Triggering in Nicaragua
Abstract Strain partitioning in oblique convergent margins results in margin‐parallel shear in the overriding plate. Margin‐parallel shear is often accommodated by margin‐parallel strike‐slip faults proximal to active volcanic arcs. Along the Nicaraguan segment of the Central American Forearc (CAFA) in the Cocos‐Caribbean plate convergent margin, there are no well‐expressed right‐lateral faults that accommodate CA‐CAFA relative motion. Instead, historical earthquakes and mapped fault orientations indicate that the ∼12 mm/yr of dextral motion is accommodated on arc‐normal, left‐lateral faults (i.e., bookshelf faults). We investigate three upper‐plate earthquakes; the 10 April 2014 (Mw6.1), 15 September 2016 (Mw5.7), and 28 September 2016 (Mw5.5), using Global Position System co‐seismic displacements and relocated earthquake aftershocks. Our analyses of the three earthquakes indicate that the 10 April 2014 earthquake ruptured an unmapped margin‐parallel right‐lateral fault in Lago Xolotlán (Managua) and the September 2016 earthquakes ruptured arc‐normal, left‐lateral and oblique‐slip faults. These earthquakes represent a triggered sequence whereby the 10 April 2014 earthquake promoted failure of the faults that ruptured in September 2016 by imparting a static Coulomb stress change (ΔCFS) of 0.02–0.07 MPa. Likewise, the 15 September 2016, earthquake additionally promoted failure (ΔCFS of 0.08–0.1 MPa) on sub‐parallel faults that ruptured in two subsequent earthquakes. We also present an instance of magma‐tectonic interaction whereby the 10 April 2014 earthquake dilated (10s of μStrain) the shallow magmatic system of Momotombo Volcano, which led to magma injection, ascent, and eruption on 1 December 2015, after ∼100 years of quiescence.
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- PAR ID:
- 10388460
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Solid Earth
- Volume:
- 127
- Issue:
- 12
- ISSN:
- 2169-9313
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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