The contribution of an urban gravity survey to the determinable perspective of Athens city (Greece) underground structur
- PDF / 42,031,762 Bytes
- 20 Pages / 595.276 x 790.866 pts Page_size
- 17 Downloads / 161 Views
The contribution of an urban gravity survey to the determinable perspective of Athens city (Greece) underground structure Spyridon Dilalos1 · John D. Alexopoulos1 Received: 8 June 2020 / Accepted: 28 August 2020 © Springer Nature Switzerland AG 2020
Abstract An urban gravity survey with more than 1120 measurements was carried out in order to adumbrate the deeper subsurface of Athens city basin. The aim was to gather quantitative information of the subsurface structure derived from the acquisition of gravity measurements. At first, a gravity base network has been established for the data collection. The standard data reduction has been carried out along with an additional Building Correction that has been calculated due to the urban characteristics. Subsequently, the residual anomaly was isolated with the contribution of the Fourier filters. The Euler deconvolution has been applied, with two different techniques, providing depth solutions for the residual maps. Based on these maps, we managed to retrieve quantitative information for the depths of anomalous sources, ranging between 500 and 3760 m. Moreover, unconstrained three-dimensional density models of the area have been constructed in order to obtain a good image of the subsurface, up to depths of 4500 m. For each three-dimensional density model, we provide a couple of images; one illustrating only the structures of lower densities and one other only with the structures of higher densities, in an effort to delineate better the tectonic structures. Finally, two geophysicalgeological profiles (2.75D) have been constructed, along which the geotectonic regime of the subsurface seems to be adumbrated in a better way. Major known tectonic structures of Athens basin have been identified beneath the surface. Keywords 2.75D Interpretative sections · Three-dimensional density models · Euler deconvolution depths · Gravity bases · Urban gravity measurements
1 Introduction The metropolis city of Greece is located in Athens basin, where 4 million people live and work. Taking into consideration the major damage caused by the devastating earthquake of 7th September 1999 (Mw = 5.9R), the need for further and deeper investigation of the geological structure of the subsurface came up. Especially in such urban and fully residentially developed areas, the knowledge on the existence of concealed active faults is absolutely valuable. The damage distribution of an earthquake is known to depend on the tectonic pattern of the area. A small problem arises due to the fact that the artificial
surfaces (buildings, roads, bridges etc.) dominate along Athens, making the geological research more difficult. The geophysical methods can overcome this difficult situation by retrieving information for the deep subsurface. Taking into account the land cover data presented in Fig. 1, provided by CORINE 2012 project [28], the areas of artificial surfaces cover a 54.5% of our study area [21]. The land gravity survey seems the most suitable method for the deep geotectonic investigation. Gravity mea
