Precise measurements help gauge Pacific Northwest\u27s Earthquake potential

Except for the recent rumblings of a few moderate earthquakes and the eruption of Mt. St. Helen\u27s, all has been relatively quiet on the Pacific Northwestern front. The Cascades region in the Pacific Northwest, a sporadically active earthquake and volcanic zone, still has great seismic potential [Atwater, 1987], as comparisons with other subduction zones around the world have shown [Heaton and Kanamori, 1984]. Recent tsunami propagation models [Satake, 1996] and tree ring studies suggest that the last great Cascadia earthquake occurred in the winter of 1700 A.D. and had a magnitude of −8.9. The North Cascades or Wenatchee earthquake followed in 1872. With an estimated magnitude greater than 7, it was the largest earthquake in the written history of Washington and Oregon

History and tectonic implications of low-angle detachment faults and orogen parallel extension, Picentini Mountains, Southern Apennines fold and thrust belt, Italy

Late Miocene to Pliocene movement on low-angle extensional faults within the internal Southern Apennines orogenic belt was superposed on an earlier, Miocene imbricate thrust stack. The low-angle faults formed within the interior of the belt during orogen parallel extension as thrust imbrication continued in the foreland. Extreme tectonic thinning defines discrete structural domains of hyperextension which are linked by a complex system of extensional and transcurrent faults. Some of the best examples of hyperextension structures in the Southern Apennines are exposed in the Picentini Mountains. In this area, detailed mapping, fault-kinematic analysis, and excellent stratigraphic control contributed to the construction of restorable cross sections and forward models of deformation. With these constraints, it is possible to document extensional displacement on shallowly dipping supercrustal faults whose orientation is a primary feature and is not due to later tilting. During movement, upper plate rocks were disarticulated by listric and planar normal faults that soled into a ramp-flat detachment system. The depth of the basal detachment increased in the direction of upper-plate motion and ranged from 5 to 10 km. Displacement on the low-angle detachment was accompanied by block tilting in the upper plate assemblage, incisement and excisement of the upper and lower plate rocks as fault trajectories changed through time, and the progressive cataclasis of hanging wall and footwall assemblages. Preexisting thrusts were only locally reactivated during extension, and faults emanating from the underlying decollement systems cross the imbricated thrust sheets at moderate to high angles. Longitudinal extension resulted in thinning of the thrust stack to less than half the original thickness and had a cumulative magnitude of between 200 and 250% (beta > 2)

The Hazard Exposure of the Maltese Islands

International comparisons of disaster risk frequently classify Malta as being one of the least hazard exposed countries. Such rankings may be criticised because: (1) they fail to take into account historic increases in population and its seasonal variation; (2) they are based on inadequately researched and incomplete historical catalogues of damaging events and (3), for small island states like Malta, they do not take into account the implications of restricted land area, which can be disproportionately impacted by even small hazardous events. In this paper, we draw upon a variety of data to discuss disaster risk in the Maltese Islands. In particular, the notion that Malta is one of the ‘safest places on earth’ is not only misleading, but also potentially dangerous because it engenders a false sense of security amongst the population. We argue that Malta is exposed to a variety of extreme events, that include: the distal effects of major earthquakes originating in southern Italy and Greece, plus their associated tsunamis; major ash producing eruptions of Mount Etna (Sicily), and their putative impacts on air transport; storm waves; coastal/inland landslides; karstic collapse; flooding and drought. In criticising international rankings of the islands’ exposure, we highlight the issues involved in formulating hazard assessments, in particular incomplete catalogues of extreme natural events. With Malta witnessing swelling resident, seasonal (i.e. tourist) plus foreign-born populations, and increases in the urban area, further research into hazards is required in order to develop evidence-based policies of disaster risk reduction (DRR)