PERFORMANCE OF SITE VELOCITY PREDICTION IN SUNDALAND

Global Positioning System (GPS) technique has been extensively implemented in determination of crustal deformation globally. With the ability of providing solution up to milimeter (mm) level, this technique has proven to provide a precise estimate of site velocity that represents the actual motion of tectonic plate over a period. Therefore, this study aims to evaluate the site velocity estimation from GPS-derived daily position of station, respective to the global plate motion model and predicted site velocity via Least-Squares Collocation (LSC) method within the tectonically active region of Sundaland. The findings have indicated that stations with precise velocity estimates were consistent with global plate model and predicted velocity, with velocity residuals of 5 mm – 10 mm. However, stations that were severely impacted by continuous earthquake events such as in Sumatra were believed to be induced by the impact with consistently large velocity residuals up to 37 mm. Following the outcomes, this study has provided an insight on the post-seismic decay period plate motion which are induced by continuous tectonic activities respective to modelled plate motion.

Developing Landslide Hazard Scenario of Kashmir Himalaya from the Historical Events

Kashmir Himalaya being a rugged and tectonically active zone has complex, unstable geology along with steep slopes, creating a favorable environment for landslide hazards, especially along the National Highway (NH-44) that connects the Vale of Kashmir with the rest of India. The historical landslide database for the whole country has not yet been developed and the data provided by various government organizations are often very limited because most of the time local and small-scale landslide events do not get recorded, thus, leading to misinterpretations. The present study focuses on retrieving the information on landslide events and their impacts to develop a comprehensive database for the period from 1990 to 2020 in Jammu and Kashmir, emphasizing Jammu-Srinagar National Highway (NH-44). A hotspot analysis tool (Getis-ord-Gi* algorithm) was used to understand the spatial distribution and concentration of the events throughout the region. The annual and seasonal analysis of the 739 landslide events reported in the valley for the selected period suggests an increasing trend causing 1000 fatalities and 267 injuries. The findings show that out of 20 districts, 16 are relatively more exposed to landslides and the socio-impact induced by landslides was found more along the NH-44 with 303 landslide occurrences reported in 260 days in the past three decades having a high intensity of damage and loss. The results of this study are expected to be of potential use for developing a Landslide Early Warning System (LEWS) and for mitigating the impacts of landslides in the Kashmir Himalaya.

Accumulation of a Last Deglacial Gravel Layer at Diexi, Eastern Tibetan Plateau and its Possible Seismic Significance

Tectonic and climatic process controlling gravel accumulation in tectonically active regions is the subject of active debate. In this study, the formation mechanism of a gravel layer in the Diexi lacustrine section, eastern Tibetan Plateau, was investigated using mutually validated dating methods and detailed analysis of sedimentary processes. Optically stimulated luminescence (OSL) and accelerator mass spectrometry (AMS) 14C dating show that the gravel layer in the Diexi section accumulated at approximately 16.79 ka BP. The sedimentary characteristics of the gravel layer and the contact between upper and lower strata indicate that the formation of the Diexi gravel layer was triggered by an earthquake rather than by a debris flow caused by torrential rain. And the result based on the intensity attenuation model are consistent with the characteristics of frequent large earthquakes in Diexi area. Detailed analysis of satellite images and sedimentary characteristics of the gravel layer provide evidence for an ancient landslide, which may be related to the gravel layer at Muer village (to the north of the Diexi section). Overall, this study reconstructs a gravel event at approximately 16.79 ka BP and has important theoretical and practical significance for understanding the formation mechanism of gravel deposits and analysing seismic events through gravel accumulation.

Coastal erosion in sandy beaches along a tectonically active coast: The Chile study case

Coastal erosion in 45 sandy beaches covering nearly 2000 km along the tectonically active Chilean coast is assessed during the last four decades. The historical analysis is based on the assessment of decadal changes of the shoreline position extracted from topographic surveys, aerial photographs, satellite images and survey maps using the DSAS software. Results show that 80% of the sites presented erosion rates (>−0.2 m/y), 7% beaches accreted (>0.2 m/y) while 13% remained stable. Eroded beaches include headland bay beaches, embayed and pocket beaches. A discussion on the possible causes explaining these results is conducted. While changes in offshore wave climate are spatially smooth within the region, relative mean sea level changes are highly variable and modulated by tectonic activity; the reduction of the sediment supply explains erosion rates in few cases.

Tsunamis in the Greek Region: An Overview of Geological and Geomorphological Evidence

The Greek region is known as one of the most seismically and tectonically active areas and it has been struck by some devastating tsunamis, with the most prominent one being the 365 AD event. During the past decade significant research efforts have been made in search of geological and geomorphological evidence of palaeotsunamis along the Greek coasts, primarily through the examination of sediment corings (72% of studies) and secondarily through boulders (i.e., 18%). The published data show that some deposits have been correlated with well-known events such as 365 AD, 1303 AD, the Minoan Santorini Eruption and the 1956 Amorgos earthquake and tsunami, while coastal studies from western Greece have also reported up to five tsunami events, dating as far back as the 6th millennium BC. Although the Ionian Islands, Peloponnese and Crete has been significantly studied, in the Aegean region research efforts are still scarce. Recent events such as the 1956 earthquake and tsunami and the 2020 Samos earthquake and tsunami highlight the need for further studies in this region, to better assess the impact of past events and for improving our knowledge of tsunami history. As Greece is amongst the most seismically active regions globally and has suffered from devastating tsunamis in the past, the identification of tsunami prone areas is essential not only for the scientific community but also for public authorities to design appropriate mitigation measures and prevent tsunami losses in the future.

Integrative geochronology calibrates the Middle and Late Stone Ages of Ethiopia’s Afar Rift

The Halibee member of the Upper Dawaitoli Formation of Ethiopia’s Middle Awash study area features a wealth of Middle and Later Stone Age (MSA and LSA) paleoanthropological resources in a succession of Pleistocene sediments. We introduce these artifacts and fossils, and determine their chronostratigraphic placement via a combination of established radioisotopic methods and a recently developed dating method applied to ostrich eggshell (OES). We apply the recently developed 230Th/U burial dating of OES to bridge the temporal gap between radiocarbon (14C) and 40Ar/39Ar ages for the MSA and provide 14C ages to constrain the younger LSA archaeology and fauna to ∼24 to 21.4 ka. Paired 14C and 230Th/U burial ages of OES agree at ∼31 ka for an older LSA locality, validating the newer method, and in turn supporting its application to stratigraphically underlying MSA occurrences previously constrained only by a maximum 40Ar/39Ar age. Associated fauna, flora, and Homo sapiens fossils are thereby now fixed between 106 ± 20 ka and 96.4 ± 1.6 ka (all errors 2σ). Additional 40Ar/39 results on an underlying tuff refine its age to 158.1 ± 11.0 ka, providing a more precise minimum age for MSA lithic artifacts, fauna, and H. sapiens fossils recovered ∼9 m below it. These results demonstrate how chronological control can be obtained in tectonically active and stratigraphically complex settings to precisely calibrate crucial evidence of technological, environmental, and evolutionary changes during the African Middle and Late Pleistocene.

Evolution of eastern Tibetan river systems is driven by the indentation of India

The main rivers that originate from the Tibetan Plateau are important as a resource and for the sedimentary and biogeochemical exchange between mountains and oceans. However, the dominant mechanism for the evolution of eastern Tibetan river systems remains ambiguous. Here we conduct geomorphological analyses of river systems and assess catchment-average erosion rates in the eastern Tibetan Plateau using a digital elevation model and cosmogenic radionuclide data. We find that major dividing ranges have northeast oriented asymmetric geometries and that erosion rates reduce in the same direction. This coincides with the northeastward indentation of India and we suggest this indicates a primarily tectonic influence on the large-scale configuration of eastern Tibetan river systems. In contrast, low-level streams appear to be controlled by fluvial self-organization processes. We propose that this distinction between high- and low-order channel evolution highlights the importance of local optimization of optimal channel network models in tectonically active areas.

Deformation of soft sediments and evaporites in a tectonically active basin: Bay St. George sub-basin, Newfoundland, Canada

The Bay St. George sub-basin of SW Newfoundland, part of the larger late Paleozoic Maritimes basin, formed under the influence of strike-slip faulting and the movement of evaporites. New stratigraphic correlations between Newfoundland and other late Paleozoic sub-basins illustrate the effects of both basement and salt movement. Coastal outcrops show complex combinations of synsedimentary, salt-related, and tectonic structures. Map relationships and dramatic thickness contrasts in the Tournaisian Anguille Group indicate that a large, concealed, NE–striking normal growth fault (Ship Cove fault) controlled sedimentation; the exposed Snakes Bight fault originated as a hanging-wall splay. Structures formed during, or soon after deposition include soft-sediment folds, boudins, clastic dykes, and millimetre-scale diapiric bulb structures, formed by overpressuring and liquidization of sediment. These suggest that the sub-basin was tectonically active throughout deposition. Evaporite-related deformation is recorded in the Visean Codroy Group and overlying strata. Comparisons between outcrop and subsurface suggests that significant amounts of evaporite were removed from exposed sections by halokinesis and solution. Complex outcrop relationships indicate salt welds, and suggest that units of the upper Codroy and overlying Barachois groups represent fills of minibasins that subsided into thick evaporites. Field relationships suggest tectonic inversion deposition related to E-W dextral strike slip motion that affected the entire Maritimes basin in the Serpukhovian, producing reverse-sense offsets and contractional folds. Many of the structures in the Bay St. George sub-basin, previously interpreted as post-depositional and purely tectonic, were formed by deformation of unlithified sediment and ductile evaporites during basin development.

Soils of mountain floodplains in the zone of tectonic joints of Mongol-Okhotsk Orogenic Belt (Mongolia)

New data on the soils of mountain floodplains in the tectonic joints zone of the Mongol-Okhotsk Orogenic Belt on the example of the Upper Kerulen Basin are presented. Soil diversity is mostly determined by sedimentation conditions and drainage of the parent rocks. There are alluvial–humus (Fluvisol (Humic)), mucky–humus (Folic Fluvisol), dark–humus (Fluvisol (Mollic)), dark–humus gley (Gleyic Fluvisol) and dark–humus saline soils (Sodic Gleyic Fluvisol (Mollic)) were diagnosed. Tectonic movements of the earth’s crust lead to the appearance of shaftlike linear dams, blocking river flow through the valley. So, the Kerulen river changed the direction of the channel and go beyond the depression, embedding into its mountain frame. Current seismicity impact on soils appears locally at tectonically active positions of epigenetic areas, close to outputs of saline underground deep waters, in the form of surface soil salinity and hydrometamorphism.

Volcano hazard and surveillance in Costa Rica

Costa Rica hosts ten volcanic complexes and is highly tectonically active due to its location at the interaction between the Cocos, Nazca, and Caribbean plates and the Panama microplate. Three of the five historically active volcanoes had frequent eruptions in 2019. The institutions in charge of monitoring the volcanoes of Costa Rica are the Observatorio Vulcanológico y Sismológico de Costa Rica from Universidad Nacional (OVSICORI-UNA) and the Red Sismológica Nacional (RSN: UCR-ICE that groups the Escuela Centroamericana de Geología from the Universidad de Costa Rica, and the Observatorio Sismológico y Vulcanológico de Arenal y Miravalles from the Instituto Costarricense de Electricidad; acronyms ECG, UCR, OSIVAM, and ICE). These institutions are focused on the most dangerous volcanoes, i.e. those closest to the Great Metropolitan Area (2.2 million inhabitants), which includes San José (the capital), and those near hydroelectrical and geothermal plants. In 2020, those institutions operated a network of. 59 seismic stations on volcanoes, 5 infrasound stations, 25 permanent GPS sites, 2 permanent DOAS, 3 permanent MultiGAS, 13 webcams, and performed systematic analyses in geochemistry and petrology laboratories. Those institutes routinely communicate results with the authorities in charge of crisis management nationally and internationally (Comisión Nacional de Prevención de Riesgos y Atención de Emergencias and Volcanic Ash Advisory Centre, respectively) and are always looking for more scientific collaborations. Costa Rica alberga diez complejos volcánicos y presenta una elevada actividad sísmica debido a su ubicación dentro de un marco tectónico complejo, donde interactúan las placas del Cocos, Nazca, Caribe y la microplaca de Panamá. Tres de los cinco volcanes históricamente activos han tenido frecuentes erupciones durante el 2019. Los institutos que vigilan los volcanes de Costa Rica son el Observatorio Vulcanológico y Sismológico de Costa Rica (OVSICORIUNA) y la Red Sismológica Nacional (RSN: UCR-ICE que agrupa a la Escuela Centroamericana de Geología de la Universidad de Costa Rica y al Observatorio Sismológico y Vulcanológico del Arenal y Miravalles del Instituto Costarricense de Electricidad, acrónimos en orden: ECG, UCR, OSIVAM e ICE). Estos institutos se enfocan principalmente en los volcanes que representan un alto riesgo para la capital San José y la Gran Área Metropolitana, en el centro de Costa Rica (2.2 millones de habitantes), y aquellos cerca de centrales hidroeléctricas y geotérmicas. La vigilancia se apoya en una red de 59 estaciones sísmicas, 5 medidores de infrasonido, 25 sitios GPS permanentes, 2 DOAS, 3 MultiGAS permanentes, 13 cámaras web y análisis sistemático de muestras en los laboratorios de geoquímica y petrología. Estas instituciones comunican sus resultados de forma rutinaria a las autoridades a cargo de la gestión de peligros nacionales e internacionales (Comisión Nacional de Prevención de Riegos y Atención de Emergencias y Volcanic Ash Advisory Centre, respectivamente), y permanecen en la búsqueda permanente de colaboraciones científicas.