No abstract

The monitoring of rock glaciers plays a relevant role in relation to natural hazards in high mountain environments. Due to the climate warming, mountain permafrost is thawing, and its degradation is influencing the triggering and the evolvement of processes such as rockfalls, landslides, debris flows and floods. Therefore, the study and monitoring of these periglacial forms have both a scientific and economic importance. We tested electrical and electromagnetic measurements along the same investigation lines, in two different sites of the Dolomites area (Northeast Italy). Electrical prospecting exploits the high resistivity contrast between frozen and non-frozen debris. However, these measurements have high logistic demands, considering the complex rock glaciers surface and the need of ground galvanic contact. For this reason, we tried to compare electrical measurements with electromagnetic contactless ones, that theoretically can be used to define the distribution of electrical resistivity in the first subsoil in a quicker and easier way. The obtained results show that the joint use of the two methods allows us to characterize a rock glacier subsoil with good confidence. Finally, the advantages and disadvantages of both the techniques are discussed.

Abstract. A novel combination of borehole temperature, borehole piezometer and cross-borehole electrical resistivity tomography (ERT) data is used to investigate changing ice and/or water contents in the creeping ice-rich Schafberg rock glacier in the Eastern Swiss Alps. Instrumentation techniques and first results are presented. The rock glacier ice is close to its melting point, and the landform has locally heterogeneous stratigraphies, ice and/or water contents and temperature regimes. The measurement techniques presented continuously monitor temporal and spatial phase changes to a depth of 12 m and should provide the basis for a better understanding of accelerating rock glacier kinematics and future water availability.

Abstract. A novel combination of borehole temperature, borehole piezometer and cross-borehole electrical resistivity tomography (ERT) data are used to investigate changing ice-/water contents in the creeping ice-rich Schafberg rock glacier in the Eastern Swiss Alps. Instrumentation techniques and first results are presented. The rock glacier is close to its melting point and has locally heterogeneous stratigraphies, ice-/water contents and temperature regimes. The measurement techniques presented continuously monitor temporal and spatial phase changes to a depth of 12 m and should provide the basis for a better understanding of accelerating rock glacier kinematics and future water availability.

Summary In this paper we present the results of an analysis of passive seismic noise recorded around the Scrovegni Chapel in Padua (Italy), using a dense 2D network with nearly 1500 autonomous seismic nodes. Surface wave tomography using the active records allowed the imaging of several structures located at a few metres depth, while the present study focuses on the processing of about 22 hours of continuous passive records. First, the ambient noise is characterized in terms of amplitude, frequency content and azimuthal distribution, in order to ensure the applicability of the interferometric method. Second, a cross-correlation analysis is performed to retrieve virtual source gathers. Third, traveltimes are extracted from virtual source gathers using the same processing sequence applied to active gathers. Fourth, Eikonal tomography is run to retrieve isotropic phase velocity maps and azimuthal anisotropy. We compare and discuss the results obtained from the active and the passive methods, and finally propose a strategy for the integration of passive and active information. The new quasi-3D shear wave velocity model obtained from the joint active and passive analysis is more accurate at depth, due to the addition of the passive low-frequency information.