SUMMARYOrigins of ancient rockslides in seismic regions can be controversial and must not necessarily be seismic. Certain slope morphologies hint at a possible coseismic development, though further analyses are required to better comprehend their failure history, such as modelling the slope in its pre-failure state and failure development in static and dynamic conditions. To this effect, a geophysical characterization of the landslide body is crucial to estimate the possible failure history of the slope. The Balta rockslide analysed in this paper is located in the seismic region of Vrancea-Buzau, Romanian Carpathian Mountains and presents a deep detachment scarp as well as a massive body of landslide deposits. We applied several geophysical techniques on the landslide body, as well as on the mountain crest above the detachment scarp, in order to characterize the fractured rock material as well as the dimension of failure. Electrical resistivity measurements revealed a possible trend of increasing fragmentation of rockslide material towards the valley bottom, accompanied by increasing soil moisture. Several seismic refraction surveys were performed on the deposits and analysed in form of P-wave refraction tomographies as well as surface waves, allowing to quantify elastic parameters of rock. In addition, a seismic array was installed close to the detachment scarp to analyse the surface wave dispersion properties from seismic ambient noise; the latter was analysed together with a colocated active surface wave analysis survey. Single-station ambient noise measurements completed all over the slope and deposits were used to further reveal impedance contrasts of the fragmented material over in situ rock, representing an important parameter to estimate the depth of the shearing horizon at several locations of the study area. The combined methods allowed the detection of a profound contrast of 70–90 m, supposedly associated with the maximum landslide material thickness. The entirety of geophysical results was used as basis to build up a geomodel of the rockslide, allowing to estimate the geometry and volume of the failed mass, that is, approximately 28.5–33.5 million m3.

中文翻译：

---

表征大规模斜坡崩塌沉积物的多项地球物理调查：在喀尔巴阡山脉巴尔塔滑坡中的应用

摘要地震区古代滑坡的起源可能存在争议，不一定是地震。某些边坡形态暗示了可能的同震发展，但需要进一步分析以更好地理解其破坏历史，例如在其破坏前状态下模拟边坡以及静态和动态条件下的破坏发展。为此，滑坡体的地球物理特征对于估计斜坡可能的破坏历史至关重要。本文分析的Balta 滑坡位于罗马尼亚喀尔巴阡山脉Vrancea-Buzau 地震区，具有很深的滑脱陡坡和大量滑坡沉积体。我们在滑坡体上应用了几种地球物理技术，以及在脱离陡坡上方的山脊上，为了表征破裂的岩石材料以及破坏的尺寸。电阻率测量揭示了滑石材料向谷底的破碎增加的可能趋势，伴随着土壤水分的增加。对沉积物进行了几次地震折射调查，并以 P 波折射层析成像和表面波的形式进行了分析，从而可以量化岩石的弹性参数。此外，在分离陡坡附近安装了一个地震阵列，以分析地震环境噪声的表面波频散特性；后者与位于同一地点的主动表面波分析调查一起进行了分析。在整个斜坡和沉积物中完成的单站环境噪声测量用于进一步揭示原位岩石上破碎材料的阻抗对比，这是估计研究区域多个位置剪切层位深度的重要参数。组合方法可以检测到 70-90 m 的强烈对比度，这可能与最大滑坡材料厚度有关。以全部地球物理结果为基础，建立了滑坡地质模型，从而可以估计破坏质量的几何形状和体积，即大约 28.5-3350 万立方米。组合方法可以检测到 70-90 m 的强烈对比度，这可能与最大滑坡材料厚度有关。以全部地球物理结果为基础，建立了滑坡地质模型，从而可以估计破坏质量的几何形状和体积，即大约 28.5-3350 万立方米。组合方法可以检测到 70-90 m 的强烈对比度，这可能与最大滑坡材料厚度有关。以全部地球物理结果为基础，建立了滑坡地质模型，从而可以估计破坏质量的几何形状和体积，即大约 28.5-3350 万立方米。