Analysis of a 150 m 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

作者：Macri P^*; Smedile A; Speranza F; Sagnotti L; Porreca M; Mochales T; Ermolli E Russo

来源：Tectonophysics, 2016, 687: 180-194.

DOI：10.1016/j.tecto.2016.09.004

• L'Aquila earthquake
• Apennine
• Continental basins
• Paleomagnetism
• Core stratigraphy
• LAQUI-CORE

LAQUI-CORE was drilled in the co-seismic subsidence depocenter shown by DinSAR images in the Bazzano sub basin after the 2009 Mw = 6.1 L'Aquila earthquake. LAQUI-CORE aimed at gathering high-resolution integrated stratigraphy and defining its relationships with the Paganica and other active faults that yielded co-seismic subsidence. Lithostratigraphy and micropaleontological analyses indicate a Late Pleistocene-Holocene fluvial-alluvial sequence, and below 41 m palustrine sediments sandwiching at 84-115 m a thick gravel package. Four C-14 ages gathered from 5 to 15 m yield calibrated ages between 6 and 41 ka BP. Paleomagnetism reveals a normal polarity above 84 m, while below the gravel package (115 m) it shows frequent polarity changes. The occurrence of intervals of clear reverse polarity testifies below 115 m the deposition during the Matuyama Chron. We conclude that the normal polarity package, down to 84 m along with the underlying gravels, were deposited at high sedimentation rate (0.46 mm/yr for the upper 15 m) during the Brunhes Chron (<0.78 Ma), and lie over a much older Early Pleistocene palustrine sequence that we correlate with the well-known Madonna della Strada Synthem (1.2-1.7 Ma). We assume that the subsidence driving the deposition of the upper normal polarity sequence was due to the activity of the Paganica and neighbour faults during the Middle-Late Pleistocene. The lack of thick volcanostratigraphic markers, widespread in colluvial sediments from the L'Aquila plain older than 460 ka, suggests a normal-polarity sedimentation onset, thus a Paganica fault activity onset, around 4001<a. The 0.25 to 0.50 mm/yr subsidence at Bazzano extrapolated by DinSAR data and paleoseismological trenching at the Paganica fault is roughly consistent with the sedimentation rate (0.46 mm/yr) yielded by radiocarbon dating in the upper LAQUI-CORE. This implies that co-seismic subsidence in the Bazzano sub-basin during Late Pleistocene-Holocene times was mainly controlled by the Paganica fault activity.

• 出版日期2016-9-26
• 单位Perugia