The Lithospheric Structure of the Central Andes (20–26°S) as Inferred from Interpretation of Regional Gravity

Götze, H.-J.; Lahmeyer, B.; Schmidt, Sabine; Strunk, S.

doi:10.1007/978-3-642-77353-2_1

Cited by 42 publications

(37 citation statements)

References 24 publications

(20 reference statements)

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“…Regional gravity studies have been carried out at the northern margin of the plateau in Peru by Fukao et al (1989) and Kono et al (1989) and in the central and southern plateau area by Götze et al (1994). Modeling of regional gravity measurements between 20 and 26…”

Section: Crustal Thickness Rheology and Isostatic Supportmentioning

confidence: 99%

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

Allmendinger

Jordan²,

Kay³

et al. 1997

Annu. Rev. Earth Planet. Sci.

809

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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Section: Crustal Thickness Rheology and Isostatic Supportmentioning

confidence: 99%

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

Allmendinger

Jordan²,

Kay³

et al. 1997

Annu. Rev. Earth Planet. Sci.

809

658

View full text Add to dashboard Cite

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“…The ANCORP steep angle reflection profile at 21°S detected the presence of a reflector at a depth of 20 km (~68.5°W) that is thought to be responsible for the Quebrada Blanca Bright Spot (QBBS in ANCORP Working Group, 2003 ) anomaly but is not observed in gravity data (e.g. Götze et al, 1994;Götze and Kirchner, 1997). Though magneto-telluric soundings do not detect the QBBS anomaly, they show an important conductivity anomaly (Altiplano Conductivity Anomaly) below the Altiplano (Brasse et al, 2002;Haberland et al, 2003).…”

Section: The Central Andes At 21°s and The Altiplano Plateaumentioning

confidence: 99%

More constraints to determine the seismic structure beneath the Central Andes at 21°S using teleseismic tomography analysis

Heit¹,

Koulakov²,

Asch³

et al. 2008

Journal of South American Earth Sciences

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A set of seismological stations was deployed in the Central Andes region along a ~600 km long profile at 21°S between Chile and Bolivia and operated for a period of almost two years, from March 2002 to January 2004. Here we present the results of the tomographic inversion for P-wave velocity anomalies, based on teleseismic data recorded at the stations. The reliability of the results has been checked by a series of synthetic tests. The tomographic images show high-velocities on the west of the profile that are indicative of cold material from the fore-arc. A low-velocity anomaly is detected at the border between the fore-and the volcanic arc where the Quebrada Blanca seismic anomaly was previously described. This anomaly might be related to the presence of fluids that originate at the cluster of earthquakes at a depth of ~100 km in the subducted plate. A strong low-velocity anomaly is detected beneath the entire Altiplano plateau and part of the Eastern Cordillera, in agreement with previous receiver function results. The Brazilian Shield is thought to be responsible for the strong high-velocity anomaly underneath the Interandean and Subandean regions.

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“…According to the computing of the isostatic residual field [Götze et al, 1994;Götze and Krause, 2002], two pronounced anomaly structures of up to 150 mGal evolve in the Antofagasta section as presented in Figure 5c. There is a rather small one south of Mejillones Peninsula at $23.6°S and a large elongated anomaly starting at 23.9°S heading southward.…”

Section: Correlation Of the B Value And Isostatic Residual Anomaly Mapsmentioning

confidence: 99%

“…[23] Götze et al [1994] and Götze and Krause [2002] interpret the IR anomalies as caused by dense batholitic bodies remaining from the Jurassic -Early Cretaceous volcanic arc system. Namely the El Cobre batholith and the Coloso coastal gabbro complex [Pichowiak, 1994] (see Figure 6a) seem to coincide with our proposed asperity structure.…”

Section: Nature Of Asperitiesmentioning

confidence: 99%

“…Assuming a gabbro type of rock for the asperities with a density of 2.96 g/cm 3 [Götze et al, 1994], we obtain a value of $2.6 g/cm 3 for the surrounding material which agrees fairly well with the density of metasediments [Ahrens and Johnson, 1995]. Estimating rigidity for the asperities and the surrounding area, we obtain m asp = 5.6 Â 10 10 N/m 2 and m sur = 4.26 Â 10 10 N/m 2 .…”

Section: Nature Of Asperitiesmentioning

confidence: 99%

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Asperity generating upper crustal sources revealed by b value and isostatic residual anomaly grids in the area of Antofagasta, Chile

et al. 2007

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[1] In our study we show that the locations of largest coseismic slip (asperities) on the fault plane of the M w = 8.0 1995 Antofagasta earthquake in Northern Chile can be mapped by the spatial distribution of the seismic b value obtained from the aftershock sequence of the megathrust earthquake. These areas of high seismic moment release and concurrent high-b values are congruent with anomalies of the gravity isostatic residual (IR) field in the Antofagasta region. They are superimposed on the seismogenic part of the north Chilean subduction zone where the strongest coupling of the upper and lower plate is expected. The IR anomalies are interpreted to be caused by large Jurassic-Early Cretaceous batholiths which intruded into the upper crust. The observed positive correlations between high seismic b values, IR anomalies, and geologic structures enable us to propose a mechanical model for the generation of the asperities in the Antofagasta region. We suggest that the batholiths in conjunction with buoyant forces acting on the subducted slab of the Nazca plate are responsible for locking the interface where the asperities are located. This implies long-term conditions for the existence of the asperity generating tectonic situation. Concequently, the asperities around Antofagasta could be stationary features, at least for several seismic cycles. Hence we propose that the IR anomalies along the north Chilean convergent margin can be used as an indicator for high moment release and slip in future large earthquakes.

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The Lithospheric Structure of the Central Andes (20–26°S) as Inferred from Interpretation of Regional Gravity

Cited by 42 publications

References 24 publications

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

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

More constraints to determine the seismic structure beneath the Central Andes at 21°S using teleseismic tomography analysis

Asperity generating upper crustal sources revealed by b value and isostatic residual anomaly grids in the area of Antofagasta, Chile

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