Please use this identifier to cite or link to this item:
http://hdl.handle.net/2122/10632
Authors: | Villani, Fabio* Sapia, Vincenzo* |
Title: | The shallow structure of a surface-rupturing fault in unconsolidated deposits from multi-scale electrical resistivity data: The 30 October 2016 Mw 6.5 central Italy earthquake case study | Journal: | Tectonophysics | Series/Report no.: | /717 (2017) | Issue Date: | 2017 | DOI: | 10.1016/j.tecto.2017.08.001 | Keywords: | Electrical methods Castelluccio di Norcia Basin Steepest gradient method |
Subject Classification: | 04.02. Exploration geophysics 05.01. Computational geophysics |
Abstract: | We report the results of a shallow electrical resistivity investigation performed across a normal fault that ruptured the surface displacingwith average ~0.05mvertical offset alluvial fan deposits (b23 kyr old) within an intermontane fault-bounded basin following the 30 October 2016Mw6.5 earthquake in central Italy.Weadopted a multi-scale geophysical approach, by acquiring three 2-D electrical resistivity tomography (ERT) profiles centred on the coseismic ruptures, and characterized by different spatial resolution and investigation depth. Below the fault scarp, the ERT models show a narrow (~10 m wide) and steeply-dipping moderately-resistive region (100–150 Ωm), which we interpret as the electrical response of the fault zone displacing layers of relatively high-resistivity (300–700 Ωm) values. We explain the electrical signature of the retrieved fault zone as due to an increment of permeability caused by coseismic fracturing, and to the subsequent water migration from adjacent shallow aquifers squeezed by compaction induced by seismic waves. By using a statistically-based classification of electrical units, we estimate that the shallowest alluvial fan layer is affected by 2.7 ± 0.9 m vertical offset,which is consistentwith the measured 2.3–2.8mmorphologic offset of the top fan surface, and suggesting a post-12 kyr throw-rate of 0.23± 0.08 mm/yr. Similarly, we evaluate a post-23 kyr throw of 5.1 ± 1.7 m, indicating a Late Pleistocene throw-rate of 0.22 ± 0.07 mm/yr, in accordance with available paleoseismic data. We further hypothesize a minimal total fault throw N30 m, which likely accrued since the Middle Pleistocene (possibly in the last 350–500 kyr). The investigated fault structure is therefore an important splay characterized by a thick and highly permeable damage zone in unconsolidated deposits, andwhich ruptured the surface during several tens of strong (M N 6) earthquakes. |
Appears in Collections: | Article published / in press |
Files in This Item:
File | Description | Size | Format | Existing users please Login |
---|---|---|---|---|
Villani and Sapia_TECTO_2017.pdf | 5.46 MB | Adobe PDF | ||
TECTO11880R2.pdf | Open Access | 8.64 MB | Adobe PDF | View/Open |
WEB OF SCIENCETM
Citations
8
checked on Feb 10, 2021
Page view(s)
260
checked on Apr 24, 2024
Download(s)
42
checked on Apr 24, 2024