Preliminary prediction of damage to residential buildings following the 21st August 2017 Ischia earthquake

On August 21st, 2017, an earthquake with duration magnitude M_d?=?4.0 and epicentre in Casamicciola Terme hit Ischia island, in the South of Italy. This event caused two fatalities and dozens of injured people. Moreover, despite the low magnitude, the earthquake produced significant damages to masonry and reinforced concrete (RC) buildings, with some partial or complete collapse of structures, in a very limited area close to the epicentre, while even at small distance from the most damaged zone the earthquake was just felt by local people and tourists. In the days after the event, discussions concerning the destructive effects of such an earthquake arose in the scientific community—as also reported by local and national media. In this paper, the seismic history of Ischia island is recalled to show and explain the peculiarity of the August 21st earthquake, which is also described in terms of ground motion and response spectra characteristics. The results of the first surveys carried out in Casamicciola Terme are reported, together with appropriate pictures, to introduce and explain the observed damage state of masonry and RC buildings in the epicentral zone. Then, data from the 15th general census of the population and dwellings (ISTAT) is used to define vulnerability classes according to the classification of the European Macrosismic Scale (EMS-98) (Grünthal, 1998). Seismic damage scenarios are then evaluated combining macro-seismic intensity values obtained using an interpolation method starting from QUEST macro-seismic survey data (Azzaro et al., 2017 ) and fragility curves for A-to-D vulnerability classes and for five damage states, from DS0 (no damage) to DS5 (collapse) trough a Monte Carlo simulation technique. The distributions of Usable, Temporarily or Partially Unusable, and Unusable buildings, which are obtained by using relationships between damage and usability judgments obtained through post-earthquake damage data collected after past seismic events, result in very good accordance with those published in September 1st, 2017 by the Department of Civil Protection, regarding a dataset of about 600 buildings.     

A first-order seismotectonic regionalization of Mexico for seismic hazard and risk estimation

The purpose of this work is to define a seismic regionalization of Mexico for seismic hazard and risk analyses. This seismic regionalization is based on seismic, geologic, and tectonic characteristics. To this end, a seismic catalog was compiled using the more reliable sources available. The catalog was made homogeneous in magnitude in order to avoid the differences in the way this parameter is reported by various agencies. Instead of using a linear regression to converts from m _b and M _d to M _s or M _w , using only events for which estimates of both magnitudes are available (i.e., paired data), we used the frequency-magnitude relations relying on the a and b values of the Gutenberg-Richter relation. The seismic regions are divided into three main categories: seismicity associated with the subduction process along the Pacific coast of Mexico, in-slab events within the down-going COC and RIV plates, and crustal seismicity associated to various geologic and tectonic regions. In total, 18 seismic regions were identified and delimited. For each, the a and b values of the Gutenberg-Richter relation were determined using a maximum likelihood estimation. The a and b parameters were repeatedly estimated as a function of time for each region, in order to confirm their reliability and stability. The recurrence times predicted by the resulting Gutenberg-Richter relations obtained are compared with the observed recurrence times of the larger events in each region of both historical and instrumental earthquakes.     

Novel mechanism of stream formation in coastal wetlands by crab–fish–groundwater interaction

A novel mechanism of stream development in coastal wetlands was observed in the form of interaction between the burrowing crab (Chasmagnathus granulata) and groundwater seepage. This process may eventually be further promoted by the predatory action of the white croaker fish (Micropogon opercularis). These so-called crab streams occur on the banks of major tidal channels in a salt marsh of the Bahía Blanca Estuary (Argentina). As the tide recedes, water is retained in the crab burrows on the marsh surface. The presence of lateral burrows produced by crab recruits promotes subterranean piping flow driven by the hydraulic head in the vertical burrow. Groundwater generally seeps along the tidal channel banks but is particularly prominent and concentrated where crab burrows perforate the banks. Where predatory attacks by the croaker fish enlarge the burrow mouths, the drainage rills become wider and deeper because more seeping water is collected in the shallow crater from where it is funnelled into the developing streams. The crab stream is then produced by water draining from the crab burrow mouth, acting initially by cut-back erosion and followed by forward erosion of the relatively unconsolidated muddy sediments.     

Processes of tidal channel development in salt and freshwater marshes

Mechanisms for the formation of creeks in tidal ?ats are rarely discussed in literature. There are some general theories about their formation but there are no data to support the evidence. It is generally believed that marshes inherit creeks from previous tidal ?ats that their plants colonize and further modify them. The aim of this paper is to present three mutually exclusive cases from marshes in Argentina where creeks are formed by either purely physical or biological–physical interactions. Except for Loyola Bay, this is the ?rst discussion of these mechanisms. They may represent special cases, but the fact that all three of them occur along the coast of Argentina, could indicate that similar cases may be found somewhere else. Copyright © 2003 John Wiley & Sons, Ltd.     

Paleoenvironmental Changes during the Last 4000 yr in the Tigray, Northern Ethiopia

In the Tigray region at the northern Ethiopian Highlands, paleoenvironmental reconstruction based on several infilled valley deposit sequences suggests that the past 4000 yr comprised three major wetter periods (ca. 4000–3500 yr B.P., 2500–1500 yr B.P., and 1000–960 yr B.P.), during which soils were formed, and two degradation episodes (ca. 3500–2500 yr B.P. and 1500–1000 yr B.P.), during which there was an increase of sediment yield from the slopes into the valleys. For the past 1000 yr, and in particular since the early 17th century, stratigraphic records together with historic chronicles suggest increasing aridity. Although difficulties arise in distinguishing between natural and human impacts, particularly in a region with a long established agricultural background, stratigraphical and proxy paleoclimatic data have indicated climate as the main controlling factor responsible for the environmental changes in the Tigray.     

APPLICATION OF A QUASI-2D HYDRO-MORPHOLOGICAL MODEL TO THE ARGENTINEAN PARAN(A) RIVER

Herein a simplified quasi-two dimensional horizontal hydro-morphological mathematical model is presented. The governing equations for the quasi-2D horizontal time-depending flow field are represented by the well-known approach of interconnected cells. New discharge laws between cells are incorporated. The model is capable of predicting temporal changes in water depth, velocity distribution,sediment transport, bed elevation, as well as water and suspended sediment exchanges between main stream and flood plains. An application of the model to the middle reach of the Argentinean Parana River is presented. Satisfactory results were obtained during model calibration, validation and application.     

Probabilistic hazard analysis of Citlaltépetl (Pico de Orizaba) Volcano, eastern Mexican Volcanic Belt

Citlaltépetl or Pico de Orizaba is the highest active volcano in the North American continent. Although Citlaltépetl is at present in repose, its eruptive history reveals repetitive explosive eruptions in the past. Its relatively low eruption rate has favored significant population growth in areas that may be affected by a potential eruptive activity. The need of some criteria for hazards assessment and land-use planning has motivated the use of statistical methods to estimate the time and space distribution of volcanic hazards around this volcano. The analysis of past activity, from late Pleistocene to historic times, and the extent of some well-identified deposits are used to calculate the recurrence probabilities of eruptions of various size during time periods useful for land-use planning.     

Geothermal map of Mexico

Silica temperatures were calculated for 326 water samples from hot and warm springs located throughout Mexico as an attempt to estimate heat flow. Available heat flow data (Smith, 1974; Smith et al., 1979) for northern Mexico were related to silica temperature data to obtain the appropriate constants for the regional conditions according to Swanberg and Morgan's equation (1979, 1980). The constants obtained are similar to those obtained for the United States, therefore heat flow can be estimated on the basis of silica temperature data. By contouring calculated temperatures a map is obtained where the main geothermal provinces are shown.