Tectonic implications of the microearthquake seismicity and fault plane solutions in southern Peru

Grange, F.; Hatzfeld, Denis; Cunningham, P.S.; Molnár, Péter; Roecker, S. W.; Suárez, Gerardo; Rodrigues, Armindo dos Santos; Ocola, L.

doi:10.1029/jb089ib07p06139

Cited by 50 publications

(15 citation statements)

References 16 publications

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“…The linear ENE-WSW-oriented concentration of events observed along the sharp bend in isodepth contours through the centre of the array implies a focusing of stress and increase in seismicity in this region, consistent with plate flexure along a smooth contortion as seen here and elsewhere (Grange et al 1984b;McCrory et al 2012). Epicentral locations from the ISC catalogue (not shown here) support these interpretations of the ENE-WSW-oriented event concentration.…”

Section: Discussionsupporting

confidence: 65%

Seismic structure in southern Peru: evidence for a smooth contortion between flat and normal subduction of the Nazca Plate

Dougherty¹,

Clayton²

2014

Geophysical Journal International

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S U M M A R YRapid changes in slab geometry are typically associated with fragmentation of the subducted plate; however, continuous curvature of the slab is also possible. The transition from flat to normal subduction in southern Peru is one such geometrical change. The morphology of the subducted Nazca Plate along this transition is explored using intraslab earthquakes recorded by temporary regional seismic arrays. Observations of a gradual increase in slab dip coupled with a lack of any gaps or vertical offsets in the intraslab seismicity suggest warping of the slab. Concentrations of focal mechanisms at orientations which are indicative of slab bending are also observed along the change in slab geometry. The presence of a thin ultra-slow velocity layer (USL) atop the horizontal Nazca slab is identified and located. The lateral extent of this USL is coincident with the margin of the projected linear continuation of the subducting Nazca Ridge, implying a causal relationship wherein increased hydration of the ridge results in the formation of the USL downdip. Waveform modelling of the 2-D structure in southern Peru using a finite-difference algorithm provides constraints on the velocity and geometry of the slab's seismic structure and confirms the absence of any tears in the slab. The seismicity and structural evidence suggests smooth contortion of the Nazca Plate along the transition from flat to normal subduction. The slab is estimated to have experienced 10 per cent strain in the along-strike direction across this transition.

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Section: Discussionsupporting

confidence: 65%

Seismic structure in southern Peru: evidence for a smooth contortion between flat and normal subduction of the Nazca Plate

Dougherty¹,

Clayton²

2014

Geophysical Journal International

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“…At the northern end of the plateau in southern Peru, crustal seismicity and young faulting also suggest approximately north-south extension (Grange et al 1984, Lavenu 1982, Sébrier et al 1985, Suárez et al 1983. At both the northern and southern ends of the plateau, the horizontal extension is oriented at 55-60…”

Section: Current State Of Stress In the Plateaumentioning

confidence: 99%

The Evolution of the Altiplano-Puna Plateau of the Central Andes

Allmendinger

Jordan²,

Kay³

et al. 1997

Annu. Rev. Earth Planet. Sci.

818

658

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▪ Abstract The enigma of continental plateaus formed in the absence of continental collision is embodied by the Altiplano-Puna, which stretches for 1800 km along the Central Andes and attains a width of 350–400 km. The plateau correlates spatially and temporally with Andean arc magmatism, but it was uplifted primarily because of crustal thickening produced by horizontal shortening of a thermally softened lithosphere. Nonetheless, known shortening at the surface accounts for only 70–80% of the observed crustal thickening, suggesting that magmatic addition and other processes such as lithospheric thinning, upper mantle hydration, or tectonic underplating may contribute significantly to thickening. Uplift in the region of the Altiplano began around 25 Ma, coincident with increased convergence rate and inferred shallowing of subduction; uplift in the Puna commenced 5–10 million years later.

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“…Schildgen et al (2009) proposed that a Tertiary episode of strike-slip and normal faulting occurred between 14 and 2.2 Ma. However, relocated microseismicity (Grange et al, 1984) and teleseismic data (Devlin et al, 2012) demonstrate present-day reverse and strike-slip components on the Lluta fault segment and more regionally for the Incapuquio fault system in the Arequipa region (Fig. 2).…”

Section: Fault Geometry and Kinematicsmentioning

confidence: 99%

“…2b) and focal mechanisms ( Fig. 2c) (M w < 5; < 20 km, Grange et al, 1984;Devlin et al, 2012). Local reverse and normal apparent surface movements are known to occur along major strike-slip faults in the forearcs of northern Chile (Victor et al, 2004) and southern Peru (Hall et al, 2012).…”

Section: Fault Geometry and Kinematicsmentioning

confidence: 99%

“…During the Eocene to Neogene, volcano-sedimentary deposits of the Moquegua group were overlain onto the Western Cordillera. This group is partly covered by the Huaylillas ignimbrite, produced Grange et al (1984) and Devlin et al (2012); the kinematics of the Incapuquio fault system are indicated by black arrows.…”

Section: Geologic and Climatic Setting Of Chuquibamba Regionmentioning

confidence: 99%

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Tectonic and climatic controls on the Chuquibamba landslide (western Andes, southern Peru)

et al. 2015

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Abstract. The contribution of landslides to the Quaternary evolution of relief is poorly documented in arid contexts. In southern Peru and northern Chile, several massive landslides disrupt the arid western Andean front. The Chuquibamba landslide, located in southern Peru, belongs to this set of large landslides. In this area, the Incapuquio fault system captures the intermittent drainage network and localizes rotational landslides. Seismic activity is significant in this region with recurrent M w 9 subduction earthquakes; however, none of the latest seismic events have triggered a major landslide. New terrestrial cosmogenic dating of the Chuquibamba landslide provides evidence that the last major gravitational mobilization of these rotational landslide deposits occurred at ∼ 102 ka, during the Ouki wet climatic event identified on the Altiplano between 120 and 98 ka. Our results suggest that wet events in the arid and fractured context of the Andean forearc induced these giant debris flows. Finally, our study highlights the role of tectonics and climate on (i) the localization of large Andean landslides in the Western Cordillera and on (ii) the long-term mass transfer to the trench along the arid Andean front.

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Tectonic implications of the microearthquake seismicity and fault plane solutions in southern Peru

Abstract: Using recordings from 15 portable instruments and six permanent stations operated during two field investigations of microearthquakes in southern Peru, we determined locations of 888 shallow and intermediate depth earthquakes and 56 fault plane solutions.

Cited by 50 publications

References 16 publications

Seismic structure in southern Peru: evidence for a smooth contortion between flat and normal subduction of the Nazca Plate

Seismic structure in southern Peru: evidence for a smooth contortion between flat and normal subduction of the Nazca Plate

The Evolution of the Altiplano-Puna Plateau of the Central Andes

Tectonic and climatic controls on the Chuquibamba landslide (western Andes, southern Peru)

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