The 151 m deep borehole LAqui-core was drilled in the co-seismic subsidence depocenter, shown by INSAR images in the Bazzano sub-basin (south-western part of the middle Aterno basin), after the 2009 Mw=6.1 earthquake that struck the historical city of L’Aquila (Abruzzi, central Italy). The LAqui-Core (Firb-Abruzzo) Project aimed to investigate the stratigraphic and geometric architecture of the middle Aterno continental basin, and to define its relationship with the local system of active faults. The core contains continental Holocene and Quaternary sediments subdivided into two main sequences separated by an erosional discontinuity. The upper sequence consists of a 41 m thick interval of fluvial-alluvial silt and sands, interbedded with metric intervals of rounded gravel, while the lower sequence consists of palustrine clays and sands sandwiching a 30 m thick interval of coarse gravel deposit between 83 and 115 m depth as suggested by the pollen and ostracods content. We carried out on selected samples distributed along the core and high-resolution paleomagnetic and rock magnetic measurements on continuous u-channel samples. Natural remanent magnetization (NRM), anhysteretic remanent magnetization (ARM), magnetic susceptibility (k) were measured at 1-cm spacing using a 2G Cryogenic magnetometer, and a set of rock magnetic parameters were computed as proxies for rock magnetic variations. The sediments carry a well-defined characteristic remanent magnetization (ChRM), isolated between 15 and 40 mT AF steps. The ChRM is of constant normal polarity down to ca. 83 m depth, with paleomagnetic inclination values oscillating around 57° and with magnetite as main magnetic carrier. Below 115 m depth the paleomagnetic data show frequent polarity changes. We interpret these polarity changes as artefacts due to the widespread occurrence of greigite in addition to magnetite. Despite this complexity, the occurrence of intervals of clearly reverse polarity indicate that this interval is older than the Brunhes-Matuyama transition. The integrated analysis of lithostratigraphy, paleomagnetism and rock magnetism, palinology, ostracoda and radiometric data on the LAqui-Core allow to reconstruct a detailed stratigraphy of the continental deposits the middle Aterno basin and provide original age constraints to define its temporal evolution

Analysis of a 150m sediment core from the co-seismic subsidence depocenter of the 2009 Mw=6.1 L'Aquila earthquake (Italy): Implications for Holocene-Pleistocene tectonic subsidence rates and for the age of the seismogenic Paganica fault system / Macrì, P.; Smedile, A.; Speranza, F.; Sagnotti, L.; Porreca, M.; Mochales, T.; RUSSO ERMOLLI, Elda. - In: TECTONOPHYSICS. - ISSN 0040-1951. - 687:(2016), pp. 180-194. [10.1016/j.tecto.2016.09.004]

Analysis of a 150m sediment core from the co-seismic subsidence depocenter of the 2009 Mw=6.1 L'Aquila earthquake (Italy): Implications for Holocene-Pleistocene tectonic subsidence rates and for the age of the seismogenic Paganica fault system

RUSSO ERMOLLI, ELDA
2016

Abstract

The 151 m deep borehole LAqui-core was drilled in the co-seismic subsidence depocenter, shown by INSAR images in the Bazzano sub-basin (south-western part of the middle Aterno basin), after the 2009 Mw=6.1 earthquake that struck the historical city of L’Aquila (Abruzzi, central Italy). The LAqui-Core (Firb-Abruzzo) Project aimed to investigate the stratigraphic and geometric architecture of the middle Aterno continental basin, and to define its relationship with the local system of active faults. The core contains continental Holocene and Quaternary sediments subdivided into two main sequences separated by an erosional discontinuity. The upper sequence consists of a 41 m thick interval of fluvial-alluvial silt and sands, interbedded with metric intervals of rounded gravel, while the lower sequence consists of palustrine clays and sands sandwiching a 30 m thick interval of coarse gravel deposit between 83 and 115 m depth as suggested by the pollen and ostracods content. We carried out on selected samples distributed along the core and high-resolution paleomagnetic and rock magnetic measurements on continuous u-channel samples. Natural remanent magnetization (NRM), anhysteretic remanent magnetization (ARM), magnetic susceptibility (k) were measured at 1-cm spacing using a 2G Cryogenic magnetometer, and a set of rock magnetic parameters were computed as proxies for rock magnetic variations. The sediments carry a well-defined characteristic remanent magnetization (ChRM), isolated between 15 and 40 mT AF steps. The ChRM is of constant normal polarity down to ca. 83 m depth, with paleomagnetic inclination values oscillating around 57° and with magnetite as main magnetic carrier. Below 115 m depth the paleomagnetic data show frequent polarity changes. We interpret these polarity changes as artefacts due to the widespread occurrence of greigite in addition to magnetite. Despite this complexity, the occurrence of intervals of clearly reverse polarity indicate that this interval is older than the Brunhes-Matuyama transition. The integrated analysis of lithostratigraphy, paleomagnetism and rock magnetism, palinology, ostracoda and radiometric data on the LAqui-Core allow to reconstruct a detailed stratigraphy of the continental deposits the middle Aterno basin and provide original age constraints to define its temporal evolution
2016
Analysis of a 150m sediment core from the co-seismic subsidence depocenter of the 2009 Mw=6.1 L'Aquila earthquake (Italy): Implications for Holocene-Pleistocene tectonic subsidence rates and for the age of the seismogenic Paganica fault system / Macrì, P.; Smedile, A.; Speranza, F.; Sagnotti, L.; Porreca, M.; Mochales, T.; RUSSO ERMOLLI, Elda. - In: TECTONOPHYSICS. - ISSN 0040-1951. - 687:(2016), pp. 180-194. [10.1016/j.tecto.2016.09.004]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11588/646257
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