特別セミナー 2013/05/28


日時: 2013年5月28日(火) 15:30-17:00
場所: 地震火山研究センターセミナー室(E411)
講演者: Lauro Chiaraluce博士
      National Eartqhake Centre, Istituto Nazionale di Geofisica e Vulcanologia
講演タイトル: Fault architecture and mechanics investigated with high-resolution earthquake locations: from seismic sequences to near fault observatories.





Abstract:

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, 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 (NL) where state of the art observational systems are installed. There are three main requirements for the NL: 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 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 minimum detection network capability in an area characterised by a very high background seismic rate, allows us to consider a low-magnitude event as a local mainshock.vv


紹介および感想:

Lauro Chiaraluce博士は,イタリア・INGV(Instituto Nationale di Geofisica e Vulcanologia)の研究員で,国内の地震観測にも積極的に関わりながら地震活動のモニタリングを通じた研究を行っています.今回のセミナーでは,大地震の発生域であるアペニン山脈地域に焦点を当て,膨大な観測データから地震学的なアプローチにより複雑な断層システムの構造を高精度に推定した結果をご紹介いただきました.また,これらの結果に基づいて,断層間相互作用や,地震の発生と間隙流体の関わり,断層の破壊強度とも深く関わることが期待される断層帯の幅に関する統計的な分析結果などもお話しいただき,大変興味深いセミナーとなりました.

地震火山研究センター助教 寺川寿子



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