Tsunami hazard in the Eastern Mediterranean: strong earthquakes and tsunamis in Cyprus and the Levantine Sea

A modern tsunami catalogue has been compiled for the region of Cyprus-Levantine Sea in which 24 certain or possible local tsunamis are listed from antiquity up to the present time, while six regional tsunamis, generated in the Hellenic arc, are documented which affected the region. Another set of 13 doubtful events not included in the catalogue are discussed. Tsunami intensities k and K were re-evaluated using the classic 6-grade and the new 12-grade intensity scales, respectively. The strongest tsunamis reported in the region of interest are those of 551 AD, 749, 1068, 1201, 1222, 1546 and 1759, all occurring along the Levantine coast from Gaza northward, with the exception of the 1222 wave which occurred in the Cyprean arc. The causative earthquakes, however, occur on land and are associated with the left-lateral strike-slip Levantine rift and, as such, remain unexplained. In this paper we speculate on the mechanism of these events. A second tsunami zone follows the Cyprean arc, where the situation of subaqueous seismogenic sources favours the generation of tsunamis by co-seismic fault displacements. Submarine or coastal earth slumping, however, may be an additional tsunamigenic component. Based on historical data, the average tsunami recurrence in the Cyprus-Levantine Sea region is roughly estimated to be around 30 years, 120 years and 375 years for moderate (k/K ≥ 2/3), strong (k/K ≥ 3/5) and very strong (k/K ≥ 5/8) events, respectively. The rate of tsunami occurrence equals 0.033, 8.3 × 10⁻³ and 2.7 × 10⁻³ events/year for intensity k/K ≥ 2/3, 3/5 and 5/8, respectively. For a Poissonian (random) process the probabilities of observing at least one moderate, strong or very strong tsunami are 0.28, 0.01 and 3 × 10⁻³ within 1 year, 0.81, 0.34 and 0.13 within 50 years and 0.96, 0.56 and 0.24 within 100 years, respectively. The tsunami potential in the Cyprus-Levantine Sea area is low relative to other Mediterranean tsunamigenic regions. However, the destructiveness of some historical events indicates the need to evaluate tsunami hazard by all available means. In addition, remote tsunamigenic sources, such as those of 1303 and 1481 in the eastern Hellenic arc, are able to threaten the coasts of the Cyprus-Levantine region and, therefore, such regional tsunamis should be taken into account in the evaluation of the tsunami risk of the region.     

Interpretation of a two-point flux stencil for skew parallelogram grids

Control-volume formulations for elliptic equations often use two-point flux stencils, even for skew grids. Any two-point flux stencil may be interpreted as a multipoint flux stencil. This yields a definition of the permeability (or conductivity) tensor. Formulas for calculating the permeability tensor, based on the user-specified quantities in the two-point flux stencil, are given. Numerical test examples demonstrate the validity of the derivation.      

Three-dimensional sedimentary architecture of Quaternary sand and gravel resources: a case study of economic sedimentology (SW Germany)

Quaternary sands and gravels form important, yet often highly heterogeneous economic deposits. Detailed 3-D analysis of the sedimentary structure and stratigraphy of these deposits allows for an accurate estimation of exploitable material. This paper presents a case study in SW Germany reconstructing the 3-D distribution of glacial sediments based on a high-resolution, process-orientated sedimentary facies classification and lithostratigraphy integrated within the geo-modelling package gOcad. Situated along the maximal ice-extent of the Rhine glacier during the last glaciation, the study area is characterised by a morphologically prominent terminal moraine and its associated sandur, which form the stratigraphically youngest sediments of a glacial basin, partially exposed in two gravel pits. These outcrops helped to reconstruct the complex sedimentary architecture of the northern part of the glacial basin. The regional analysis is based on core data, as well as geoelectric and geomagnetic surveys. All data were integrated into km-scale, high-resolution geological 3-D models, depicting the large-scale dynamics of multiple glacier advances and retreats during the Early to Late Pleistocene. These models allow quantifying the thickness and volume distribution of exploitable sandy gravel and help to evaluate the occurrence of non-exploitable interbedded diamicton horizons. The high quality and quantity of gravels particularly north of the terminal moraine classifies the investigated area as very prospective for raw materials exploitation in the future.     

The wavelet method as an alternative for reducing ionospheric effects from single-frequency GPS receivers

The ionospheric effect is one of the major errors in GPS data processing over long baselines. As a dispersive medium, it is possible to compute its influence on the GPS signal with the ionosphere-free linear combination of L1 and L2 observables, requiring dual-frequency receivers. In the case of single-frequency receivers, ionospheric effects are either neglected or reduced by using a model. In this paper, an alternative for single-frequency users is proposed. It involves multiresolution analysis (MRA) using a wavelet analysis of the double-difference observations to remove the short- and medium-scale ionosphere variations and disturbances, as well as some minor tropospheric effects. Experiments were carried out over three baseline lengths from 50 to 450 km, and the results provided by the proposed method were better than those from dual-frequency receivers. The horizontal root mean square was of about 0.28 m (1σ).     

Road Surface Modeling and Representation from Point Cloud Based on Fuzzy Clustering

A scheme for an automatic road surface modeling from a noisy point cloud is presented. The normal vectors of the point cloud are estimated by distance-weighted fitting of local plane. Then, an automati...     

Application of Refactoring and Design Pattern in Land Information System Development

The unceasing change problem of land information systems can be resolved through the refactoring and design pattern. To promote the implementation of design pattern and refactoring methods in developin...     

Three-dimensional simulations of air flow and momentum transfer in partially harvested forests

In order to predict wind loading on trees (canopy height h) in partially harvested forests, it is necessary to characterize air flow and momentum transfer in progressively more complex patterns where groups of trees (or aggregates) are retained. In this study, we used large-eddy simulation to explore the effects of aggregate size, inter-aggregate spacing, and the ratio between the aggregate size and inter-aggregate spacing on air flow and momentum transfer. Forty-five grid points across an aggregate were needed to achieve an adequate level of turbulence. Using grid sizes of h/15 throughout was too viscous for the smaller aggregates. Vertical and horizontal flow deflection by the leading aggregates sheltered some of the downstream aggregates to varying degrees where turbulence increased for subsequent rows. The number of rows of protected aggregates decreased as aggregate dimensions and the space between aggregates increased. A theoretical treatment of time-dependent wind is presented for the lead aggregate and a simulation case is presented for the case of a gust of reduced wind passing through the aggregate pattern. The leading aggregate responded with decreasing moment for decreasing ambient wind speed as predicted by theory. However, downwind aggregates experienced substantial increases in bending moment. The overall results of the disruptive aspects of time dependence agrees with arguments regarding the role of irrotational (potential) flow to this problem. Our treatment of retention pattern design is only a first step and further research suggestions are presented.