Brian N. Damiata

The Viking Age settlement pattern of Langholt, North Iceland: Results of the Skagafjörður Archaeological Settlement Survey

An archaeological survey of the Viking Age settlement pattern in the Langholt region of North Iceland suggests that being early in this sequence conferred tremendous advantages to the settlers of this previously uninhabited landscape. Many of the farms established during the settlement of Iceland (which began about a.d. 870) are in use today. However, accessing the Viking Age landscape is difficult. In Langholt the earliest layers of most farmsteads are buried under a thousand years of occupational debris, while the abandoned sites have been covered by extensive soil deposition. Here we report on our coring and test excavation results that outline Viking Age farmstead location, establishment date, and maximum size by the end of the Viking Age. There is a strong correlation between farmstead size and establishment date. This correlation suggests that during the rapid settlement of Iceland, the farmsteads established by earlier settlers were wealthier and that wealth endured.

Gravitational attraction of solids of revolution: Part 1: Vertical circular cylinder with radial variation of density

Integral expressions are derived for the vertical component of gravitational attraction arising from vertical circular cylinders and horizontal circular disks with radial variation of density. The expressions contain a single elliptic integral of either the first or second kind and are evaluated easily by numerical integration. Various closed-form solutions are obtained for special cases. For constant density, the expressions reduce to well-known solutions as well as approximations that are based on the solid angle and line element, thus providing a unified theme for the derivations of those solutions and approximations. Numerical implementation is discussed in terms of practical application.

Gravitational attraction of solids of revolution: Part 2: General expressions

A general integral expression is formulated for the gravitational attraction due to any solid of revolution based on the attraction of vertical, semi-infinite, circular, cylindrical shells. The expression accommodates solids with radial variation of density. For solids with constant density, further generalization to arbitrary orientation is made through coordinate transformation that considers both vertical and radial components of attraction. Special solutions for solids with simple geometry are listed. Practical applications are demonstrated by forward gravity modelling the effects of volcanic islands (cylindrical core bounded by an outer exponentially trending surface) and inclined finite-length cylinders. Corresponding expressions for the magnetic case are discussed in terms of using Poissons relation.

GROUND DEFORMATION OF ZAKYNTHOS ISLAND (WESTERN GREECE) OBSERVED BY PSI AND DGPS

Ground deformation studies based on Differential GPS (DGPS) measurements and Permanent Scatterers InSAR (PSI)* analysis using ERS (1992-2000) and ENVISAT (2003-2010) radar data have been conducted on Zakynthos Island (Western Greece) covering the period 1992 to 2012. These results were compared, validated and integrated with geological, geotectonic and seismological data to evaluate possible pre-earthquake deformation process, and the present tectonic regime. The PSI results indicate that a slight subsidence had occurred during the period 1992-2000, while uplift has mainly observed in 2003-2010. DGPS results for 2005-2006 indicated strong opening of the southern part of the island, while in the period 2006-2012 the amplitude of deformation is relatively smaller. The occurrence of the seismic outbreak that took place offshore to the south of Zakynthos during 2005-2006 may have contributed to the different deformational pattern as revealed by the ERS and ENVISAT PSI products, and also elucidate the DGPS results.

Ground deformation study of KOS island (SE Greece) based on Squee-SAR™ interferometric technique

The SE part of the Hellenic Volcanic Arc (HVA), including Kos, Yali and Nisyros islands, is geodynamically very active and of high tectonic unrest, where the largest volumes of volcanic products were emitted during the past 160,000 years. The SqueeSAR™ Interferometric technique based on ENVISAT radar data has been applied in Kos to spatially and temporally study the ground deformation for the period 2003-2010. The observed LOS velocity field, with values ranging between -4 to +4 mm/yr, combined with small standard deviation velocity (<;1.4 mm/yr) and acceleration (-0.5 to 1.5 mm/yr2) values reveal an almost linear type of ground deformation. These small velocity values in conjunction with intermediate seismicity occurring only off-shore, indicate ground deformation of aseismic local character. The strongest subsidence is associated with local geothermal areas, as well as rural areas due to intense water pumping. Motions along the main faulting zones have also been clearly identified.