#	Pagina
attuale pagina	/open-h2020/projects/208335/results.html

Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - SMR (Seismic Moment and Recurrence (SMR) using Luminescence Dating Techniques)

Teaser

Summary

The aim of the SMR project is to explore the use of the luminescence techniques to date fault rock related materials which are directly associated with past earthquake events and develop detailed methodologies on the use of the luminescence dating techniques for palaeoseismology and neotectonic studies.
To achieve this, it is essential the assessment of the parameters that would allow â€œzeroingâ€ of the luminescence signal of minerals found on fault rock related materials, which is a prerequisite for the use of luminescence dating techniques.
SMR investigates the zeroing potential of the luminescence signal of minerals by employing experimental simulations of tectonic processes in the laboratory, combined with luminescence dating of samples collected from real fault zones (not subject to laboratory simulations). The project also includes independent cross-checks by ESR dating to validate the ages obtained using luminescence dating.
The objectives of the SMR project are:
1) The identification of brittle fault zone materials suitable for luminescence dating using a novel multi-analytical approach which combines microstructural, mineralogical and chemical analyses.
2) The assessment of the resetting potential of the luminescence signal of minerals contained in materials found on faults brittle zone.
3) The development of detailed protocols (analytical procedures) on the use of luminescence dating techniques, suitable specifically for fault rock related materials.
4) The establishment of earthquakes past recurrence times and waiting times (based on luminescence dating techniques) for a number of faults.

SMR aims to answer crucial questions of geoscientists, which are the absolute dating of faults past seismic events and their sequence by providing a detailed approach and methodology on the use of luminescence dating techniques, thus contributing to the efforts for earthquakes prediction. The results of the project could ultimately affect the way earthquake prediction and risk assessment research is carried out in Europe and worldwide, creating bridges between different fields of knowledge for infrastructure planning and design but also for mitigation measures. Further, the methodologies which are developed will become part for geo-hazards evaluations, adding to the efforts for effectively addressing societal safety, thus contributing to a reduction in the risk posed to
European population, both in terms of human and financial losses. From the perspective of the HORIZON 2020, the objectives of the SMR project are well-suited to fully contribute to the enhancement of European Union competitiveness and excellence in the thematic areas of â€œSecure
societiesâ€, (â€œH2020 work programmeâ€; Natural Hazards: Towards risk reduction science and innovation plans at national and European level).

Work performed

For achieving the aims and objectives of the SMR project, the work performed during the first 24 months included:
A) The collections of a number of samples from five faults (Mattinata Fault-Italy, Rodopos fault in Crete-Greece, Arkitsa fault zone-Central Greece, Nojima Fault-Japan and Arima Fault-Japan), as these faults represent different characteristics in relation to the material developed in their brittle zones which in turn affect the mechanical strength and stability of faults differently.
B) The characterization of the collected fault zone materials - microstructural, mineralogical and chemical analyses. Petrographic thin sections were prepared and the microstructural characteristics of the bulk brittle material samples were observed by Scanning Electron Microscope (SEM). Quantitative chemical analyses on polished thin sections were made using Energy-Dispersive Spectrometry (EDS). Mineralogical analyses by X-ray diffraction (XRD) were made to observe different mineral structures. This gave the opportunity to identify and characterize brittle fault zone materials that contain suitable minerals for luminescence dating (e.g., quartz and feldspar). This also gave the opportunity to examine the thermal history (as a result of faulting) of the samples as minerals illite and chlorite undergo changes on heating.
C) The assessment of the zeroing potential of the luminescence signal of minerals contained in materials found on faults zone. Stress-simulations in the laboratory were performed using a Low Strain Shear and Rotary (LSSR) and a shear High-Velocity Rotary Friction (HVRF) machine, to investigate the frictional processes and the dynamic strength of the samples, and also the mechanical results and the developing microstructures, within the brittle material layer. Experiments were conducted at varying slip rates, displacements, normal stresses and ambient conditions, to test the dependence of the strain distribution. Mechanical data (e.g., frictional resistance, shear stress, shortening and dilation, etc.) as well as the temperature close to the slip surface were recorded during the experiments. Microstructural, chemical, and mineralogical analyses as described above were conducted again to investigate the stress-simulation deformation effects. Following the stress-simulation experiments, samples were chemically treated to isolate the minerals suitable for luminescence measurements (quartz and feldspar) and their luminescence signals were measured using a number of different luminescence techniques (OSL, TT-OSL, TL, IRSL). Luminescence investigated â€œzeroingâ€ of the luminescence signals, as a result of the different stresssimulation conditions (e.g., successively increasing stress, varying slip rates).

Final results

SMR has already progress beyond the state of the art. In previous attempts to date fault zones, the issue was mainly studied indirectly, dating the stratigraphic fractured geological units which were formed after a seismic event and not the brittle materials (gouges, breccias, mylonites) that arise at the moment of the movement of the tectonic units and the deformation of a fault. Even in ideal cases, when the technique was applied to deformed materials, the reliability of the results could not be established due to the lack of independent cross-checks. SMR approach includes independent cross-checks (by ESR dating) to validate the ages obtained using luminescence dating techniques, something that has not been done before. An additional element that goes beyond the state of the art is the combination of: a) the examination of the luminescence characteristics of fault rock related materials which have been subject to experimental simulations of tectonic processes in the laboratory and b) luminescence measurements of the same materials which has not been used in the simulation experiments. Thus, allowing the investigation of the luminescence signal resetting effect. It is expected that at the end of the SMR project, new luminescence dating analytical procedures will have been developed, providing clear guidance on directly dating fault rock related materials, thus facilitating the assessment of the seismic histories of seismically active areas and eventually earthquake forecasting.