We provide a database of the coseismic geological surface effects following the Mw 6.5 Norcia earthquake that hit central Italy on 30 October 2016. This was one of the strongest seismic events to occur in Europe in the past thirty years, causing complex surface ruptures over an area of >400 km2. The database originated from the collaboration of several European teams (Open EMERGEO Working Group; about 130 researchers) coordinated by the Istituto Nazionale di Geofisica e Vulcanologia. The observations were collected by performing detailed field surveys in the epicentral region in order to describe the geometry and kinematics of surface faulting, and subsequently of landslides and other secondary coseismic effects. The resulting database consists of homogeneous georeferenced records identifying 7323 observation points, each of which contains 18 numeric and string fields of relevant information. This database will impact future earthquake studies focused on modelling of the seismic processes in active extensional settings, updating probabilistic estimates of slip distribution, and assessing the hazard of surface faulting.

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We documented the porosity, permeability, pore geometry, pore type, textural anisotropy, and capillary pressure of carbonate rock samples collected along basin-bounding normal faults in central Italy. The study samples consist of one Mesozoic platform carbonate host rock with low porosity and permeability, four fractured host rocks of the damage zones, and four fault rocks of the fault cores. The four fractured samples have high secondary porosity, due to elongated, connected, soft pores that provide fluid pathways in the damage zone. We modeled this zone as an elastic cracked medium, and used the Budiansky-O'Connell correlation to compute its permeability from the measured elastic moduli. This correlation can be applied only to fractured rocks with large secondary porosity and high-aspect ratio pores. The four fault rock samples are made up of survivor clasts embedded in fine carbonate matrices and cements with sub-spherical, stiff pores. The low porosity and permeability of these rocks, and their high values of capillary pressure, are consistent with the fault core sealing as much as 77 and 140 m of gas and oil columns, respectively. We modeled the fault core as a granular medium, and used the Kozeny-Carmen correlation, assigning the value of 5 to the Kozeny constant, to compute its permeability from the measured porosities and pore radii. The permeability structure of the normal faults is composed of two main units with unique hydraulic characteristics: a granular fault core that acts as a seal to cross-fault fluid flow, and an elastic cracked damage zone that surrounds the core and forms a conduit for fluid flow. Transient pathways for alongfault fluid flow may form in the fault core during seismic faulting due to the formation of opening-mode fractures within the cemented fault rocks.

[1] We studied the structures and stable isotope geochemistry of carbonate fault rocks in four normal faults of central Italy. The faults juxtapose Meso-Cenozoic carbonates of the footwalls against continental basins of the hanging walls. Footwall rocks exposed along fault scarps have been exhumed from depths of $1 km. The fault rocks are systematically arranged in each fault and can be separated into five distinct domains. Farthest from the main fault contact are undeformed host rock and fractured host rock (domain 1). Progressively closer to the fault contact, in the core of the fault, are gouge (domain 2), cataclasite (domain 3), and cement-dominated horizons with planar slip surfaces (domain 4). Thin horizons of brecciated hanging wall sediments (domain 5) are adjacent, and locally accreted, to the footwall. Structural and stable isotope data are consistent with compartmentalization of fluid in the faults during exhumation. The data are most consistent with these fluids being predominantly evolved meteoric water rather than fluids from the mantle, crustal magmas, and/or devolatilizing carbonate rocks. Meteoric water infiltrated domains 4 and 5 of the faults, either from hanging wall sediments or directly at the land surface. The gouge and cataclasites of domains 2 and 3 were impermeable barriers to movement of meteoric water into domain 1 and undamaged host rocks of the footwall. The results of this study do not support models of earthquake nucleation and rupture that envision large volumes of deep-seated fluids passing upward through shallow portions of these seismogenic faults.