8 May, 2015 – Seminar

When: 11am on Friday May 8th, 2015
Where: DIAS Merrion Square Library

Speaker: Dr. Luisa Valoroso and Dr. Lauro Chiaraluce from INGV-National Earthquake Center, Rome, Italy.
Title: Fault architecture and mechanics investigated with high-resolution earthquake locations: from seismic sequences to near fault observatories.
Description: A key feature to investigate earthquake mechanics is the detailed description and characterisation of fault zone structure and kinematics. In 15 years, by improving the available datasets and earthquake location techniques, we have upgraded the resolution of our observing system by more than one order of magnitude. We progressed from the reconstruction of the geometry of the main fault segments at the kilometre scale (e.g. Colfiorito fault, 1997), to the identification and description of secondary structures tens of meters long (e.g. L’Aquila fault, 2009). Currently fault anatomy retrieved by seismicity distribution finally resembles the degree of complexity observed by field geologists on fault outcrops, showing multiple fault splays, bend and cross fault intersections, dilatation jogs and horsetail structures. We observe seismological damage zones characterized by the same thickness and fracture (e.g. earthquakes) density decay, similar to the geological ones. The availability of very large and high-resolution earthquake location catalogues also allows for the investigation of seismicity pattern evolution and fault permeability basing on robust statistical approaches. Therefore only high-resolution data can help in this ambitious challenge of describing and modelling the multi-scale processes which control the faulting phenomena and seismicity evolution. At the same time, we are aware that we need data produced through a multidisciplinary approach. That is why for the past ten years there has been a worldwide commitment to identify Natural Laboratories where state of the art observational systems are installed. There are three main requirements for these areas: must have a reasonably small extension, there must be active faults on it and it must have a regular occurrence of earthquakes.
The area we selected is in Italy is located along the Northern Apennines where the existence of a very low angle normal fault (dip 15°), named Alto Tiberina fault is documented. There, we built a geophysical network (The Alto Tiberina Neat Fault Observatory, TABOO; http://taboo.rm.ingv.it/), composed by tens of co-located seismic and geodetic stations. The extraordinary minimum detection network capability (around ML -0.2) in an area characterised by a very high background seismic rate (r=7.30e−04 eqks/day*km2), allows us to consider a low-magnitude event as a local mainshock. We will present TABOO preliminary results and how we intend to enhance our Near Fault Observatory to create a multi-sensor network able to broaden the range of monitored parameters potentially related to the earthquake preparatory and nucleation phase.