Ambient Noise Measurements to Constrain the Geological Structure of the Güevéjar Landslide (S Spain)

Abstract

The reactivation of very large landslides may cause severe damage to society. Its prevention and management requires detailed information on the geometry and structure of these landslides, but the use of standard techniques (boreholes) may be prohibitive from an economic point of view. To overcome these difficulties, geophysical techniques are of special interest because they allow for studying very large areas at a reasonable cost. In this paper, we present a case study wherein the analysis of ambient noise allowed us to produce a model of a large landslide near Granada (southern Spain). The geometry and location of the failure zone, as well as the assessment of the state of involved materials, were estimated by combining two available boreholes and different geophysical techniques (downhole tests and the spectral analysis of ambient noise, horizontal to vertical spectral ratios (HVSR) and the frequency-wavenumber (f-k) methods). The results have allowed us to differentiate between values within the landslide mass with respect to those of stable materials, and to perform for the first time a comprehensive geological model of this unstable mass. Differences were also observed within the landslide mass (earth flow vs. slide zones), which are attributed to differences in the degree of alteration and the disturbance of the internal structure of materials constituting the landslide mass. These results show that techniques based on the measurement of ambient noise are of special interest for studying very large, highly remolded landslide masses.

A Comparative Analysis for Defining the Sliding Surface and Internal Structure in an Active Landslide Using the HVSR Passive Geophysical Technique in Pujilí (Cotopaxi), Ecuador

“…The records obtained in HVSR single-station tests may provide more reliable data for determining the V s at each measured point [21,40]. Nevertheless, considering a constrained interpretation model of their results (ellipticity curve from HVSR records), V s distribution can be consistently defined under the tested points [21,50]. To conduct the inversion procedure, starting ellipticity curves were analyzed using free DINVER software, part of GEOPSY package [68][69][70].…”

“…Table 5 presents the values obtained for each HVSR survey point measured in the area. The direction was calculated as the value perpendicular to the azimuth, which was expected to correspond to the general trend of the internal structures [10,13,21]. The The results showed one or two peaks of the HVSR-ellipticity curve, marked by the high amplification value (blue-band-color contoured intervals are used on these scales, with the contouring scale varying on every graph).…”

“…Table 5 presents the values obtained for each HVSR survey point measured in the area. The direction was calculated as the value perpendicular to the azimuth, which was expected to correspond to the general trend of the internal structures [10,13,21]. The directivity graphs in Figure 8 only consider half of the circumference because the values were symmetric [69].…”

Slope Stability Analysis to Correlate Shear Strength with Slope Angle and Shear Stress by Considering Saturated and Unsaturated Seismic Conditions

“…For instance, diatomite species increased both residual and peak shear strength of soil [32]. Similarly, the occurrence of landslides is a geohazard problem that affects many regions of the world [33]. Landslides may occur due to natural events such as earthquakes, rain, volcanic eruption and also by manmade changes to the ground and slopes.…”

Design and Implementation of a Wireless Recorder System for Seismic Noise Array Measurements

“… The possibility of remote management by connecting the server to the Internet. The system has been designed to work with up to 10 sensors covering an area of approximately 250 m in diameter, which satisfies the needs required in previous seismic microzonation studies, e.g., [ 21 , 36 , 37 , 38 ]. …”