Interplay of Holocene surface faulting and climate in the Central Po Plain, Italy

Understanding the recent events marking the late Quaternary history of the Po Plain (N-Italy) is of overriding importance to decipher the record of depositional versus erosional phases, and their interplay with climatic, tectonic, and human forcing. We reconstructed the structural setting and chronostratigraphy of a Holocene succession crosscut by a thrust fault located south of Montodine (Cremona, Italy) within the Po Plain. The fault shows a maximum displacement up to one meter. Radiocarbon dating fixes a minimum age of 11.9 cal ka BP for the postglacial river entrenchment and constrains the fault movement age between 5.9 and 3.4 cal ka BP. Undeformed Late Medieval coarse gravels cover the faulted succession. Due to the outcrop position, lying above the buried frontal thrusts of the Southern Alps and North Apennines, we propose that faulting results from secondary surface effects induced by seismic shaking. We discuss two main mechanisms, both related to lateral spreading, that can result in the formation of reverse faults close to the surface. The Soncino area, recording one of the strongest historical earthquakes of the central Po Plain (1802), is considered as a possible source for seismic shaking. The results of this study are a contribution for the assessment of the potential seismic hazard in one of the most populated regions of Europe.

Understanding the fractures connectivity control in NEB field, South Sumatra Basin: from seismic to geomechanics and Its Implication for further fractured basement exploration

The natural fractured basement reservoirs become an obsessive target in Jabung Block. Currently, there are two wells drilled in the block that targeting fractured basement reservoir. They are the NEB Base-1 well that located in western part of the NEB Field and the NEB Base-2 well which located 7 kilometers away to the East of NEB Base-1 well. The first well was technically success, however NEB Base-2 well shows no indication of hydrocarbon influx during the test. Interestingly, the fractures development in both wells shows almost the same condition of fractures orientation, dip-magnitude and fractures intensity. Furthermore, each fracture in both wells can be correlated into several zones, as they indicate similar fracture set orientation at each zone. These findings create a big question, why the similar fractures characters show a very different test result? This study is intended to have that question answered with the idea to focus on the following two workflows: the first is to re-evaluate the previous works starting from re-picking the seismic fault in detail. The second is to analyze the relationship between geomechanical forward modelling result with the structural evolution in Jabung Block through sandbox modelling. The geomechanical forward modelling in the NEB Field imply the critical stress stated that was predominantly located in the western part or within the NEB Base-1 area., This result is strongly correlate with the new basement fault map which shows an intensive faulting in the western area, and is characterized by couples of synthetic-antithetic Riedel shear as a result of the strike-slip faulting. In addition, the sandbox modelling shows a major oblique-slip fault movement was observed within the western area. Therefore, it can be concluded that the intensive strike slip fault plays an important role to enhance the connectivity between fault and fracture to the hydrocarbon storage as shown in the result of NEB Base-1 well. This idea could be used as a guidance to explore another fractured basement prospect within the block.

Imaging ground surface deformations in post-disaster settings via small UAVs

Small unmanned aerial vehicles have been seeing increased deployment in field surveys in recent years. Their portability, maneuverability, and high-resolution imaging are useful in mapping surface features that satellite- and plane-mounted imaging systems could not access. In this study, we develop and apply a workplan for implementing UAV surveys in post-disaster settings to optimize the flights for the needs of the scientific team and first responders. Three disasters caused by geophysical hazards and their associated surface deformation impacts were studied implementing this workplan and was optimized based on the target features and environmental conditions. An earthquake that caused lateral spreading and damaged houses and roads near riverine areas were observed in drone images to have lengths of up to 40 m and vertical displacements of 60 cm. Drone surveys captured 2D aerial raster images and 3D point clouds leading to the preservation of these features in soft-sedimentary ground which were found to be tilled over after only 3 months. The point cloud provided a stored 3D environment where further analysis of the mechanisms leading to these fissures is possible. In another earthquake-devastated locale, areas hypothesized to contain the suspected source fault zone necessitated low-altitude UAV imaging below the treeline capturing Riedel shears with centimetric accuracy that supported the existence of extensional surface deformation due to fault movement. In the aftermath of a phreatomagmatic eruption and the formation of sub-metric fissures in nearby towns, high-altitude flights allowed for the identification of the location and dominant NE–SW trend of these fissures suggesting horst-and-graben structures. The workplan implemented and refined during these deployments will prove useful in surveying other post-disaster settings around the world, optimizing data collection while minimizing risk to the drone and the drone operators.

Identifikasi Deformasi Tektonik Aktif Berdasarkan Ekstraksi Kelurusan Morfologi dan Seismisitas di Sukabumi, Jawa Barat

ABSTRAK Pusat gempa bumi di Sukabumi telah membentuk deformasi bawah permukaan dan kini terekam juga di permukaan. Hal itu termanifestasi melalui geomorfologi kelurusan gawir dan sungai. Ekstraksi kelurusan-kelurusan akibat deformasi geologi tersebut dapat digunakan untuk mengidentifikasi deformasi tektonik aktifnya. Tujuan penelitian ini adalah untuk mengetahui hubungan antara struktur sesar aktif dengan arah dominan kelurusan di daerah penelitian. Metode Edge Enhancing Filtering digunakan untuk menginterpretasi kelurusan secara manual dan semi-otomatis. Data geospasial kelurusan diekstraksi menggunakan formula Sastratenaya untuk mengetahui kronologi kelurusan yang terbentuk. Hasil analisis menggunakan formula Sastratenaya menunjukkan kelurusan-kelurusan yang terekam melalui olah data peta DEM, yaitu segmen 1 berarah N315°E dan segmen 2 berarah N10°E yang diinterpretasikan sebagai hasil reaktivasi sesar. Hal ini dapat diinterpretasikan bahwa Sesar Cimandiri, yang merupakan sesar aktif dengan pergerakan oblique-slip sinistral N88°E/85° rake 33°, memengaruhi arah dua segmen kelurusan di daerah penelitian wilayah Sukabumi, Jawa Barat.ABSTRACT The epicenter of the earthquake in Sukabumi has formed subsurface deformation which is now also recorded on the surface area. This is manifested through the geomorphology of the scarp and river lineaments. Extraction of lineaments produced by geological deformation can be used to identify its active tectonic deformation. The research objective is to determine the relationship between the active fault structure and the dominant direction of lineaments in the study area. The Edge Enhancing Filtering method is used to interpret lineaments manually and semi-automatically. The lineament geospatial data was extracted using the Sastratenaya formula to determine the chronology of the lineaments formed. The Sastratenaya formula results showed the lineaments recorded by DEM images data processing, the first segment direction is N315°E and the second is N10°E, both are interpreted as the result of fault reactivation. It can be interpreted that the Cimandiri Fault, which is an active fault that has an N88°E/85° rake 33° sinistral oblique-slip fault movement, affects the lineaments direction of two segments in the research area of Sukabumi, West Java.

Analysis of Damage Mechanism of Tunnel Lining Structure under the Coupling Action of Active Fault

To reveal the failure mechanism of tunnel structure under active fault movement, based on the pseudostatic elastoplastic finite element method, the failure modes of the tunnel lining are studied under different movement ratios of strike-slip faults and thrust faults with 45° dip angle by using numerical simulation. The results show that the range of significant lining failure section can be determined according to any direction of the coupling fault movement decomposition direction, and the damage effect is determined by the overall movement amount of the coupling fault. The significant damage area of the lining under the action of the coupling fault is the same as the area of deformation, which mainly manifests as tensile failure. Compressive failure occurs in the boundary area between the fracture zone and the hanging wall and foot wall. The plastic strain is the largest in the area where the arch waist and the arch bottom intersect. The development of tunnel lining plastic zone under coupling fault is from arch top and arch bottom to both sides of the arch waist. The development of the plastic zone under active fault is mainly determined by the form of fault with a large ratio. The research results can provide a reference for the design and safety evaluation of tunnel crossing active faults.

Deglaciation and neotectonics in South East Raasay, Scottish Inner Hebrides

Changes in the physical landscape of SE Raasay at the end of the last Quaternary glaciation are examined. The area is marked by a major fault system defining the Beinn na Leac Fault Block, and field survey shows this to comprise a rollover anticline in the SW, with extensional movement towards the NE along an oblique transfer fault, the Main Beinn na Leac Fault. The fault system was reactivated after the Last Glacial Maximum (the LGM). Survey of a distinctive ridge of detached scree along the Main Beinn na Leac fault shows it to have involved a single movement of at least 7.12m vertical displacement, arguably the greatest fault movement since before the Younger Dryas in Scotland. The present work confirms that the scree became detached during the Younger Dryas, but finds that it overlies a lacustrine deposit of at least 5.6m of laminated sediments from a lake which had begun to accumulate earlier. Radiocarbon dating of peat overlying the lake sediments gave 10,176 – 10,315 cal. BP, but morphological and stratigraphical evidence indicates that drainage of the lake occurred earlier and only shortly before movement of the scree. Possible causes of displacement at the fault system are briefly discussed.

Coulomb Stress Change in Ahar-Varzaghan (20121108) Earth Quakes

Understanding how the movement of faults and deformation affects such as motion-induced surface stress and strain, which is very important in seismic regions. The best way to learn about the effects of fault movement is modeled. For example, the modeling of surface displacement or deformation and the amount of damage earthquake can be estimated by the model. Coulomb stress changes can be modeled or predicted earthquake aftershocks or future Earthquakes. we employ assumptions on the orientations, rupture lengths and average slip associated with each earthquake to calculate stress changes. Using this model, we displacement, stress and strain at any depth in the Earth's surface acquired. In this study the modeling of earthquakes Mw= 6.5, Mw=6.3 Ahar-Varzaghan. The earthquakes induced displacements, strains and stresses were calculated at the surface at an average depth and its aftershocks for 10-km Ahar and 4 km Varzaghan.