The Italian CMT dataset from 1977 to the present

A seismic source zone model for the seismic hazard assessment of the Italian territory

This paper presents 1 the overall procedure followed in order to assemble the most recent pan-European strong-motion databank: Reference Database for Seismic Ground-Motion in Europe (RESORCE). RESORCE is one of the by-products of the SeIsmic Ground Motion Assessment (SIGMA; projet-sigma.com) project. RESORCE is intended to be a single integrated accelerometric databank for broader Europe to understand the regional differences in seismic hazard for improving risk studies in Europe and surrounding countries. RESORCE principally updates and extends the previous pan-European strong-motion data-bank (Ambraseys in Bollettino di Geofisica Teorica ed Applicata 45:113-129, 2004a) from recently compiled Greek, Italian, Swiss and Turkish accelerometric archives. The updates also include the earthquake-specific literature studies published in recent years. The current content of RESORCE includes 5,882 multi-component and uniformly processed accelerograms from 1,814 events and 1,540 strong-motion stations. The moment magnitude range covered by RESORCE is 2.8 Mw 7.8. The source-to-site distance interval extends to 587 km and distance information is given by the common point- and extended-source distance measures. The paper presents the current features of RESORCE through simple statistics that also quantify the differences in metadata and strong-motion processing with respect to the previous version of the pan-European strong-motion databank.

/pdf/reference-database-for-seismic-ground-motion-in-europe-2jybhvff2h.pdf

Reference database for seismic ground-motion in Europe (RESORCE)

SUMMARY

New geomorphological and structural data permitted to define the active faulting framework of the eastern Southern Alps (NE Italy). All the active faults detected in the investigated area are thrust segments of the complex thrust system, which has been responsible for the latest building of the Eastern Southalpine chain (ESC). Geomorphological investigations were performed to identify the surficial traces of recent fault activity, generally represented by gentle scarps connecting uplifted palaeolandscapes of Quaternary age with the flat and lower areas of the Venetian and Friulian plains. Surficial and subsurficial data (the latter from reflection seismic profiles) available for the investigated faults indicate that the thrusts have been responsible for the displacement of the entire wedge of Quaternary deposits. In the western sector of the investigated area, the six recognized fault segments represent portions of a 100-km-long thrust system, at the boundary between the Alpine relief and the plain areas. In the eastern sector, active tectonics is the result of parallel thrust segments, located both in the Alpine mountainous area and in the Friulian plain. The 3-D geometry of the active thrust segments has been derived from new structural surficial surveys and the interpretation of reflection seismic profiles for a total length of 1700 km. On this basis, we defined the geometry of 10 seismogenic sources whose dimensions are consistent with the occurrence of earthquakes with M≥ 6. The comparison between the source geometry and the highest intensity data point distribution of large historical earthquakes has permitted to make hypotheses on the association of past seismic events to specific seismogenic sources. This procedure indicated that no large historical events can be attributed to three sources (Montello-Conegliano, Arba-Ragogna, Medea). This may indicate an elapsed time since the last activation of more than eight centuries, based on the completeness of the historical catalogues. The available data define, therefore, sources (and related areas) for which a high level of seismic hazard may be invoked.

/pdf/seismogenic-sources-potentially-responsible-for-earthquakes-2venb2zdvh.pdf

Seismogenic sources potentially responsible for earthquakes with M≥ 6 in the eastern Southern Alps (Thiene–Udine sector, NE Italy)

Results are presented of the first airborne LiDAR survey ever flown in Europe for the purpose of mapping the surface expression of earthquake-prone faults. Detailed topographic images derived from LiDAR data of the Idrija and Ravne strike-slip faults in NW Slovenia reveal geomorphological and structural features that shed light on the overall architecture and kinematic history of both fault systems. The 1998 Mw = 5.6, and 2004 Mw = 5.2 Ravne Fault earthquakes and the historically devastating 1511 M = 6.8 Idrija earthquake indicate that both systems pose a serious seismic hazard in the region. Because both fault systems occur within forested terrain, a tree removal algorithm was applied to the data; the resulting images reveal surface scarps and tectonic landforms in unprecedented detail. Importantly, two sites were discovered to be potentially suitable for fault trenching and palaeo-seismological analysis. This study highlights the potential contribution of LiDAR surveying in both low-relief valley terrain and high-relief mountainous terrain to a regional seismic hazard assessment programme. Geoscientists working in other tectonically active regions of the world where earthquake-prone faults are obscured by forest cover would also benefit from LiDAR maps that have been processed to remove the canopy return and reveal the forest floor topography.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2006GL027014

Application of airborne LiDAR to mapping seismogenic faults in forested mountainous terrain, southeastern Alps, Slovenia

We study the 1998 Bovec-Krn mountain (Slovenia) earthquake sequence by combining hypocenters relocation, strong motion inversion, digital elevation modelling and field geology. The main shock (Ms=5.7), a 12 km right lateral strike-slip event on the Dinaric fault system, occurred on a sub-vertical fault plane. The rupture, confined between 3 and 9 km depth, with no evidence of surface faulting, propagated bilaterally within two structural barriers. The northwestern barrier is at the junction between Dinaric and Alpine structures where there is a sharp change in the geometry of faulting. The southeastern barrier is within the Dinaric system and its surface expression corresponds to the Tolminka-spring perched basin, a 1 km restraining step-over. At this site, the Bovec-Krn earthquake-fault overlaps with a 30 km strike-slip fault segment that is free of aftershocks and could be undergoing an increase of stress. This fault system represents the northern branch of the Idrija right-lateral fault.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2000GL011973

J. Bajc

Papers

The 1998 Bovec-Krn mountain (Slovenia) earthquake sequence