A morpho-tectonic approach to the study of earthquakes in Rome

Rome has the world’s longest historical record of felt earthquakes, with more than 100 events during the last 2,600 years. However, no destructive earthquake has been reported in the sources and all of the greatest damage suffered in the past has been attributed to far-field events. While this fact suggests that a moderate seismotectonic regime characterizes the Rome area, no study has provided a comprehensive explanation for the lack of strong earthquakes in the region. Through the analysis of the focal mechanism and the morphostructural setting of the epicentral area of a "typical" moderate earthquake (ML = 3.3) that recently occurred in the northern urban area of Rome, we demonstrate that this event reactivated a buried segment of an ancient fault generated under both a different and a stronger tectonic regime than that which is presently active. We also show that the evident structural control over the drainage network in this area reflects an extreme degree of fragmentation of a set of buried faults generated under two competing stress fields throughout the Pleistocene. Small faults and a present-day weaker tectonic regime with respect to that acting during the Pleistocene explain the lack of strong seismicity and imply that a large earthquake could not reasonably occur.

Research on Technology and Application of Buried Faults Identification in Urban Underground Space

With theurbanization rate's rising and three-dimensional expansion and development of urban, the identification of underground buried faults has become the key factor of earthquake risk in urban underground space and surface area. As a typical method of detecting blind faults in underground space, shallow seismic prospecting technology plays an important role in judging and avoiding potential risks such as underground faults in the process of urban expansion and site selection. In this paper, shallow seismic prospecting technology is adopted, and optimized processing technologies such as parameter test, tomographic correction, pre-stack denoising, fidelity and consistency processing, correction iteration, migration imaging, and time-depth relationship deduction are adopted. Underground faults are identified and interpreted in the studied urban area, and fault risk assessment is carried out based on fault characteristics, scale, distribution and overlying strata, thus providing suggestions for regional pattern and construction of urban planning.

Geophysical Imaging of Yellowstone’s Hydrothermal Plumbing System

Yellowstone National Park’s plumbing system linking deep thermal fluids to legendary thermal features is virtually unknown. Prevailing concepts of Yellowstone’s hydrology and chemistry are that fluids flow laterally from distal sources and emerge at the edges of lava flows and that spring chemistry reflects varying fluid source regions1,2. Here we present the first view of Yellowstone’s hydrothermal system derived from electrical resistivity and magnetic susceptibility models of airborne geophysical data3,4. Groundwater and thermal fluids containing total dissolved solids or low pH significantly reduce resistivities of porous volcanic rocks5. Low susceptibility clay sequences mapped in thermal areas6,7 and boreholes8 typically form over fault-controlled thermal fluid and/or gas conduits9-12. We show that most thermal features are located above high-flux conduits along buried faults and flow paths are similar irrespective of spring chemistry. Lateral outflow from the conduits mixes with upflow and groundwater at shallow levels in the thermal basins. Similarities between our models and those from the Taupo Volcanic Zone highlight the implication of our work beyond Yellowstone and suggest that hydrothermal systems worldwide are vertically-driven and surface geochemical variations are controlled at depth by mixing of local and distal thermal fluids and groundwater and more locally, by shallow permeability.

CHIRP-ENGINEERING SEISMIC METHOD FOR EXPLORING SEABED AND UNDERWATER STRUCTURES: OFF-SHORE WESTERN ANATOLIA

CHIRP systems are widely used in seabed sediment classification, submarine faults, positioning of marine engineering structures, pipeline geotechnical studies, platform and well area assessments, archaeological and environmental impact assessments. The resolution of the system is in the order of decimeter. In this study, the characteristics of submarine active faults, buried faults, seabed and underlying layers in the region were analyzed and interpreted by CHIRP data collected off-shore Seferihisar, Teke Peninsula and Alaçatı.

Different disaster characteristics of earth fissures and their influence factors in the Beijing plain

To analyze the generation of different ground fissure disasters, two typical ground fissures were selected. With geological survey and exploration data, the spatial characteristics of the Songzhuang and Gaoliying fissures were investigated. The different occurrence factors for the Songzhuang and Gaoliying fissures were analyzed based on geological structure and groundwater. The conclusions contain are as follows. The affected body of the Songzhuang fissure exhibits obvious tensile deformation, and it is not contact with buried faults. The fracture-affected body of the Gaoliying fissure shows obvious vertical dislocation and shear, and this is compounded with buried faults. The distribution characteristic of the Songzhuang fissure was controlled by the tectonics and the normal fault, while the buried fault not only control the distribution feature of the Gaoliying fissure but also controlled its deformation characteristic. A buried fault is the geological background for the formation of the Gaoliying fissure. The long-term exploitation of groundwater has caused the horizontal deformation of the soil and the rigid rotation of stratum in the subsidence edge. Both of them are the reason for the tensile deformation. Due to the activities of buried faults and differential subsidence in small areas, the affected bodies of the Gaoliying fissure showed vertical dislocation and shear deformation.

Characterization of Geological Structures under Thick Quaternary Formations with CSAMT Method in Taiyuan City, Northern China

A controlled-source audio-frequency magnetotelluric (CSAMT) survey was used to detect geological structures beneath the thick quaternary formation in Taiyuan, Shanxi Province, northern China. Two main CSAMT survey lines with 182 survey sites were recorded. A two-dimensional (2D) inversion technique was used to interpret the CSAMT data. The inversion results suggested that: 1) there are four main buried faults named F1, F2, F3, and F4 with dip angles about 65° across the survey line from west to east, the fault displacements of these faults are about 230 m, 180 m, 220 m and 200 m, respectively; 2) the depth of the bedrocks decrease from 1600 to 500 m along the survey lines; and 3) from top to bottom, there are four major layers in the survey area that include the upper layer with the resistivity less than 40 ohm-m represents unconsolidated sediments in the Quaternary formation, a second layer with the resistivity range from 40 to 120 ohm-m represents mudstone and sandstone, a third layer with the resistivity range from 120 to 280 ohm-m represents coal measure strata in the Permian and Carboniferous and a bottom layer with the resistivity higher than 280 Ω·m represents limestone in Ordovician. The CSAMT method is an effective technique for exploring buried fault of several hundred meters deep in metropolitan environment.