The Lemnos 8 January 2013 (M w = 5.7) earthquake: fault slip,aftershock properties and static stress transfer modeling in the north Aegean Sea

We investigate mainshock slip distribution and aftershock activity of the 8 January 2013 M _w?=?5.7 Lemnos earthquake, north Aegean Sea. We analyse the seismic waveforms to better understand the spatio-temporal characteristics of earthquake rupture within the seismogenic layer of the crust. Peak slip values range from 50 to 64 cm and mean slip values range from 10 to 12 cm. The slip patches of the event extend over an area of dimensions 16?×?16 km². We also relocate aftershock catalog locations to image seismic fault dimensions and test earthquake transfer models. The relocated events allowed us to identify the active faults in this area of the north Aegean Sea by locating two, NE–SW linear patterns of aftershocks. The aftershock distribution of the mainshock event clearly reveals a NE–SW striking fault about 40 km offshore Lemnos Island that extends from 2 km up to a depth of 14 km. After the mainshock most of the seismic activity migrated to the east and to the north of the hypocenter due to (a) rupture directivity towards the NE and (b) Coulomb stress transfer. A stress inversion analysis based on 14 focal mechanisms of aftershocks showed that the maximum horizontal stress is compressional at N84°E. The static stress transfer analysis for all post-1943 major events in the North Aegean shows no evidence for triggering of the 2013 event. We suggest that the 2013 event occurred due to tectonic loading of the North Aegean crust.     

Polyorogenic reworking of ore‐controlling shear zones at the South Range of the Sudbury impact structure: A telltale story from in situ U–Pb titanite geochronology

The post‐impact orogenic evolution of the world class Ni–Cu–PGE Sudbury mining camp in Ontario remains poorly understood. New temporal constraints from ore‐controlling, epidote–amphibolite facies shear zones in the heavily mineralised Creighton Mine (Sudbury, South Range) illuminate the complex orogenic history of the Sudbury structure. In situ U–Pb dating of shear‐hosted titanite grains by LA‐ICP‐MS reveals new evidence for shear zone reworking during the Yavapai (ca. 1.77–1.7 Ga), Mazatzalian–Labradorian (1.7–1.6 Ga) and Chieflakian–Pinwarian (1.5–1.4 Ga) accretionary events. The new age data show that the effects of the Penokean orogeny (1.9–1.8 Ga) on the structural architecture of the Sudbury structure have been overestimated. At a regional scale, the new titanite age populations corroborate that the Southern Province of the Canadian Shield documents the same tectonothermal episodes that are recorded along orogenic strike within the accretionary provinces of the Southwestern United States.     

Occurrence and40Ar/39Ar dating of a granite in Thera (Santorini,Greece)

A granite was drilled in the prevolcanic basement of Thera, an island of the Attico-Cycladic belt. It intruded the blueschist facies country rocks. K-Ar biotite ages and Ar-Ar plateau ages on two feldspars indicate rapid cooling, as all ages cluster around 9.5 Ma. Its occurrence indicates that the thermometamorphic evolution that characterizes the Attiko-Cycladic belt extends as far as Thera.

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Zusammenfassung Auf der Insel Thera, im Attiko-Kykladishen Gürtel, ist ein Granitkörper in einer Tiefe von ca. 250 m durch eine Bohrung aufgedeckt. Dieser Granitkörper ist in metamorphen Gesteinen von Blauschiefer-Facies intrudiert. K-Ar-Biotit- und Ar-Ar-Feldspat-Altersbestimmungen streuen um 9.5 Ma. Diese Alter weisen auf rasche Abkühlung des Granitkörpers hin. Es zeigt sich somit, daß die thermometamorphe Entwicklung des Attiko-Kykladischen Gürtels bis zur Insel Thera reicht.

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Résumé Un forage a été pratiqué dans un granite du socle pré-volcanique de l'île de Thera, qui appartient à la ceinture attico-cycladique. Ce granite a intrudé les roches encaissantes de facies schistes bleus. Les datations effectuées sur les biotites par la méthode K-Ar et les âges-plateau des feldspaths obtenus par la méthode Ar-Ar indiquent un refroidissement rapide, puisque tous les âges sont de l'ordre de 9,5 Ma. Ce granite montre que l'évolution thermométamorphique qui caractérise la ceinture Attico-Cycladique s'étend jusqu'à l'île de Thera.

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Thera 250 . . / / 9,5 . , . .. , Thera.

     

Organization of Emergency Response After a Major Disaster Event in an Urban Area with the Help of an Automatic Vehicle Location and Control System

The quick response of civil authorities after a major disaster event in an urban area is essential for the reduction of damages and impacts to human lives. One of the first critical problems to be solved at the very early stages of response is the optimum management of emergency vehicles and real time knowledge of the accessibility of the road network. In this article the concept of using a number of emergency vehicles as sensors for monitoring the traffic conditions in an urban area after a major disaster event is described. The fleet management system used for this taks is working with ral time DGPS. The system makes use of existing vehicle fleets in the urban area, rapidly collecting data and covering the whole road network. It records travel times with the help of the GPS system for every road segment driven through by each vehicle sensor, thus providing a digital time database from which traffic parameters can be also computed. It can be used for real time monitoring of traffic conditions under disaster or emergency situations where all the previously available data become invalid or unreliable. ? 2002 Wiley Periodicals, Inc.     

Clastic sedimentary features of beachrocks and their palaeo-environmental significance:comparison of past and modern coastal regimes

Clastic sedimentary features of beachrocks and unconsolidated deposits of parent beaches were investigated along the northern Aegean coastline（Greece） to assess their suitability in palaeo-environmental reconstruction.Twelve paired datasets were collected in the Thermaikos,Toroneos,Siggitikos and lerissos gulfs of the Chalkidiki Peninsula,the adjoining Kavala Gulf and Thassos Island,comprising beachrock cores and companion beach subsurface sediments.Particle size analyses based on univariate and bivariate statistics suggest that,during the time period of beachrock formation,depositional conditions differed distinctly from those of the modern parent beaches.The results imply difference of maturity level of beach evolution from the time of cementation（coarser materials-early stage of beach formation） to modern situation（finer materials-reworked and ’mature’ beach sediments）.Furthermore,the findings indicate increasing coastal protection due to beachrock exposure in the modern swash zone.In conclusion,it is suggested that textural analysis of beachrocks in comparison with unconsolidated sediments of the parent beach might provide information regarding differences of coastal depositional regimes and future research could focus on specific-layer analysis and comparison.     

The influence of load inclination on the undrained bearing capacity of strip footings on slopes

The effect of inclined loading on the bearing capacity of foundations on horizontal ground surface is well established and both the exact solution and simpler empirical equations are available for the calculation of the failure loads. However, for footings on or near slopes complete solutions are available only for vertical loading. This paper investigates the influence of inclined loading on the horizontal and vertical failure loads. The finite element, upper bound plasticity and stress field methods are used to examine a wide range of geometries and soil properties. The methods are first validated against known solutions for two special cases and are subsequently employed to investigate the effect of the geometrical and material properties on the failure loads and the bearing capacity load interaction diagram. Based on this investigation an empirical equation is proposed for the load interaction diagram for undrained inclined loading of footings on or near slopes.     

Assessment of freely available DSMs for automatic karst feature detection

The purpose of this work is to present the detection and qualification of natural karst depressions in southern Ksiromero, SW Aitoloakarnania Prefecture, Western Greece, by the use of freely available digital surface model (DSM) data in line with the geographical information systems—GIS. The study area is a part of the Ionian geotectonic zone whose geological background consists of the Triassic evaporates and Triassic carbonate breccias. The after-Triassic carbonate series, which consist of the Jurassic limestones, the Cretaceous limestones and the Eocene limestones, are also presented in the study area. Several DSMs such as ASTER GDEM, SRTM DEM, ALOS Global DSM, and a DSM generated from Sentinel-1 data were evaluated so as to be used for the automatic karst detection. Furthermore, a karst detection procedure applied on DSMs was performed with the aid of analogue and digital air photos. Additionally, the aforementioned procedure was applied also on DEM with the aid of digitized contours referring to topographic maps characterized by a scale of 1/50,000. All the detected features have been also validated via in situ observations. Finally, all DSMs presented herein are characterized by similar percentage of success in terms of automatic karst detection, regardless their spatial resolution and height accuracy. Their rate varies from 66 to 73%.     

Empirical relationships between aftershock area dimensions and magnitude for earthquakes in the Mediterranean Sea region

Fault dimension estimates derived from the aftershock area extent of 36 shallow depth (≤ 31 km) earthquakes that occurred in the Mediterranean Sea region have been used in order to establish empirical relationships between length, width, area and surface-wave/moment magnitude. This dataset consists of events whose aftershock sequence was recorded by a dense local or regional network and the reported location errors did not exceed on average 3–5 km. Surface-wave magnitudes for these events were obtained from the NEIC database and/or published reports, while moment magnitudes as well as focal mechanisms were available from the Harvard/USGS catalogues. Contrary to the results of some previously published studies we found no evidence in our dataset that faulting type may have an effect on the fault dimension estimates and therefore we derived relationships for the whole of the dataset. Comparisons, by means of statistical F-tests, of our relationships with other previously published regional and global relationships were performed in order to check possible similarities or differences. Most such comparisons showed relatively low significance levels (< 95%), since the differences in source dimension estimates were large mainly for magnitudes lower than 6.5, becoming smaller with increasing magnitude. Some degree of similarity, however, could be observed between our fault length relationship and the one derived from aftershock area lengths of events in Greece, while a difference was found between our regional and global fault length relationships. A calculation of the ratio defined as the fault length, derived from our relationships, to the length estimated from regional empirical relationships involving surface ruptures showed that it can take a maximum value of about 7 for small magnitudes while it approaches unity at Ms 7.2. When calculating the same ratio using instead global empirical relationships we see the maximum value not exceeding 1.8, while unity is reached at Mw 7.8, indicating the existence of a strong regional variation in the fault lengths of earthquakes occurring in the Mediterranean Sea region. Also, a relationship between the logarithms of the rupture area and seismic moment is established and it is inferred that there is some variation of stress drop as a function of seismic moment. In particular, it is observed that for magnitudes lower than 6.6 the stress drop fluctuates around 10 bar, while for larger magnitudes the stress drop reaches a value as high as 60 bar.