Future Large Earthquake Analysis of Sulawesi Island Using Satellite Images and Moment Tensor Solution Approach

Sulawesi Island is the active tectonic region, where the tectonic architecture and potential earthquake sources until now remain largely unknown. The worst earthquake, an Mw 7.5 on September 28, 2018, in Palu, Indonesia, was caused catastrophic damage to life and property. The earthquake has highlighted the urgent need to raise knowledge of the cause of possible large future earthquakes and vulnerability. The main objective for this project is to create a thorough earthquake probabilistic hazard analysis map of the region, which is presently unavailable to better prepare for future earthquakes. The neotectonic and structural map was created using was supplemented with the 30-m resolution Shuttle Radar Topography Mission, Centroid Moment Tensor (CMT) solution, and seismologic data. The results demonstrate that faulting controls the geometry and the majority of these faults are active and capable of causing medium to large magnitude earthquakes with moment magnitudes ranging from 6.2 to 7.5 from 44 seismic sources. Our results show Sulawesi's northern deformation regimes have high seismicity risk and vulnerability. This study contributes a realistic seismic source for the Sulawesi neotectonic area particularly at the northwest, north, and east deformation regime, to understand the key large future earthquakes.

On the Issues of Spatial Modeling of Non-Standard Profiles by the Example of Electromagnetic Emission Measurement Data

This paper examines the possibility of the spatial modelling of the Earth’s natural pulsed-electromagnetic-field measured values, which form a closed profile without the data inside. This geophysical method allows us to map active tectonic movement which breaches the integrity of pipes. During the experiment, 4.5 km of profiles were measured in the Admiralteysky district of St. Petersburg, Russia. Regular electromotive force (EMF) values and anomalous EMF values were obtained, ranging from 0 to 900 µV and above 900 µV, respectively. The anomalous values are associated with tectonic faults in the bedrock. The data obtained are characterized by complex spatial anisotropy associated with the development of two groups of tectonic faults of different orientations. The authors have considered the problems of the spatial modeling of the data obtained. The main problems, the solutions to which should allow the obtaining of adequate models, have been identified. Based on the analysis of the measurement results, geological features of the studied areas, as well as variography, the following possible solutions were proposed: changing the measurement technique; dividing the data array according to the main directions of anisotropy; the need to introduce additional correction coefficients. The problem revealed in this article requires further research on the basis of the obtained results, which will reduce the cost and timing of such studies, and, as a result, give an opportunity to take into account active tectonic disturbances during the construction and scheduled maintenance of underground utilities, which is especially important within the framework of the concept of sustainable development.

The northern Thessaly strong earthquakes of March 3 and 4, 2021, and their neotectonic setting

A sequence of earthquakes occurred on March 3rd and 4th in Northern Thessaly, northern Greece, associated with previously unknown, blind normal faults within the crystalline Palaeozoic basement of the Pelagonian geotectonic zone. Surficial ground deformation, such as liquefaction phenomena in fluvial plains, as well as soil fissures and rock falls, have been mapped. Geological indications of the unmapped seismic fault, i.e., reactivated shear zones, open cracks, etc., have been identified within the bedrock. Based on geological indications, the main fault projection to the surface could be considered a 15 km NW-SE trending structure and average dip of 45o to the NE. The seismic source of the main shock was modelled, and the Coulomb static stress changes calculated for receiver faults similar to the source. The determination of the active tectonic regime of the region by geodetic data and the well-known faults of NE Thessaly plain are also presented, as well as the revised historical and instrumental seismicity. This earthquake raises new concerns and challenges, revising some established views, such as the status of main stress orientations, the orientation of active tectonic structures, the occurrence of a seismogenic fault in a mountainous massif of crystalline rocks without typical geomorphological expression and the role of blind faults in Seismic Hazard Assessment.

Earthquake Swarm Analysis around Mt. Salak, West Java, Indonesia, Using BMKG Data from August 10 to November 24, 2019

Earthquake swarms commonly come approximately active tectonic and volcanic area. Interestingly, the swarm events occurred ~23 km southwest from Mt. Salak-Bogor, West Java, Indonesia, from August 10 to November 24, 2019, and were recorded by local/regional network of the Indonesian Agency for Meteorology, Climatology, and Geophysics (BMKG). Our previous study showed that in this area a destructive ML 4.6 earthquake with thrust faulting occurred on September 8, 2012. The double-difference method was applied to update the hypocenter locations from the BMKG data. In the time period of ~3.5 months, we relocated 79 swarm events with ~9.4 km depth average for local magnitude (ML) 2.2 to 4.2. The source mechanism result for selected events shows a strike-slip faulting. Our interpretation is that these swarm events are probably related to stress change due to volcano-tectonic activity.

Heterogeneity of the population of Lonicera caerulea L. in the tectonically active zone (Altai Mountains, Kurai ridge)

Depending on specific combinations of geoenvironmental factors, the micropopulations of the bluehoneysuckle in the valley of the Kuraika River (Gorny Altai) produced fruits of increased or decreased size and seednumber. The observed 3-fold higher accumulation of biologically active phenols in fruits, accompanied by the respectivedecreased accumulation in leaves, and narrower ratios of certain polyphenol classes in leaves and fruits are considered tobe the plant response to the stressing impact of environmental factors, resulting from the active tectonic processes in thestudied area of the Russian Altai.

Topographic disequilibrium, landscape dynamics and active tectonics: an example from the Bhutan Himalaya

The quantification of active tectonics from geomorphological and morphometric approaches commonly implies that erosion and tectonics have reached a certain balance. Such equilibrium conditions are however rare in nature, as questioned and documented by recent theoretical studies indicating that drainage basins may be perpetually re-arranging even though tectonic and climatic conditions remain constant. Here, we document these drainage dynamics in the Bhutan Himalaya, where evidence for out-of-equilibrium morphologies have for long been noticed, from major (> 1 km high) river knickpoints and from high-altitude low-relief regions in the mountain hinterland. To further characterize these morphologies and their dynamics, we perform field observations and a detailed quantitative morphometric analysis using χ plots and Gilbert metrics of drainages over various spatial scales, from major Himalayan rivers to their tributaries draining the low-relief regions. We first find that the river network is highly dynamic and unstable, with much evidence of divide migration and river captures. The landscape response to these dynamics is relatively rapid. Our results do not support the idea of a general wave of incision propagating upstream, as expected from most previous interpretations. Also, the specific spatial organization in which all major knickpoints and low-relief regions are located along a longitudinal band in the Bhutan hinterland, whatever their spatial scale and the dimensions of the associated drainage basins, calls for a common local supporting mechanism most probably related to active tectonic uplift. From there, we discuss possible interpretations of the observed landscape in Bhutan. Our results emphasize the need for a precise documentation of landscape dynamics and disequilibrium over various spatial scales as a first step in morpho-tectonic studies of active landscapes.

Deep oceanic submarine fieldwork with undergraduate students, an exceptional immersive experience (Minerve software)

We present the content and scripting of an active tectonic lab-session conceived for third year undergraduate students studying Earth Sciences at Observatoire des Sciences de l’Univers of Lyon. This session is based on a research project conducted on the submarine Roseau active fault in Lesser Antilles. The fault morphology is particularly interesting to map as this structure in the deep ocean is preserved from weathering. Thus high resolution models computed from Remotely Operated Vehicle videos (ROV) provide exceptional educational material to link fault morphology and coseismic displacement. This5class, composed of mapping exercises on GIS and virtual fieldwork, aims at providing basic understanding of active tectonics,and in particular active fault morphology. The work has been conducted either in a full remote configuration via 3D online models or in virtual reality (VR) in a dedicated room using the Minerve software. During the VR sessions, students were either alone in the virtual environment or participated as a full group, including the teacher (physically in the classroom or remotely, from another location), which is to our knowledge one of the first attempts of this kind in France. We discuss on the efficiency10of virtual fieldwork using VR based on feedback from teachers and students, and we conclude that VR is a promising tool to learn observational skills, subject to certain improvements which should be possible in the years to come.

Micro-displacement monitoring in caves at the Southern Alps–Dinarides–Southwestern Pannonian Basin junction

In situ micro-displacement monitoring in caves at the seismically active junction of the Southern Alps, Dinarides and Southwestern Pannonian Basin revealed active tectonic micro-deformations. The largest total vertical movement of 0.35 mm (2008–2018) occurred at Kostanjeviška Jama (Southwestern Pannonian Basin–Dinarides). Two abrupt displacements observed at that cave location correspond to pre- and post-seismic episodes in 2014 and 2015. At Pološka Jama (Southern Alps), more gradual and continuous displacement on a monitored bedding plane of 0.13 mm down-slip (2008–2018) was observed. This movement is attributed to slope relaxation as well as tectonic activity on the Julian Alps thrust fault and the seismogenic Ravne Fault, which generated earthquakes at Mw = 5.6 in 1998 and Mw = 5.2 in 2004. At Jama pri Svetih Treh Kraljih in Dinarides, activity on the Ravne Fault was shown as sinistral-horizontal (0.1 mm) and vertical (0.15 mm) movement along an E–W-oriented tectonic structure. This shallowly buried site also experienced cyclic seasonal displacements. At Županova Jama, multiple short-term horizontal dextral and sinistral strike-slip pulses (2016–2018) demonstrated active tectonic micro-deformations within the wider zone of the Dobrepolje and Želimlje faults. At Postojnska Jama, two episodes of vertical movement on a NW–SE-oriented fault are associated with earthquake swarms: the first episode was in 2010 (MLV = 3.7) and the second in 2014 (MLV = 4.3). In-cave flood events do not coincide with periods of micro-displacement activity in the studied caves, and therefore are not the drivers of the micro-displacement.

MORPHOTECTONIC EVALUATION OF SIRCH MOUNTAINS USING WATER BASIN GEOMORPHIC INDICES

Morphotectonic indices are useful instruments for investigating the effect of tectonic activity in a certain region. Calculation of these indicators using the advantages of Geographical Information System, GIS, in a large area is useful for detecting potential disorders related to active tectonics. This method is useful in regions on which few morphotectonic studies have been conducted. An example of such areas can be the watersheds of the Sirch mountainous region. The watersheds of the Sirch region located in Central Iran’s zone in the southeast of Iran are a very ideal zone to evaluate the concepts of these indicators in the prediction of the relative tectonic activity according to the investigation of drainage systems or mountain fronts. Based on the values of the calculated indices including Form Factor (FF), Compaction Coefficient (CC), Ratio of Circularity (RC), Ratio of Elongation (RE), relative Basin Height (BH), and Ruggedness Number (RN), a final indicator called Active Tectonic Indicator (ATI) is obtained. The latter is a combination of the abovementioned indicators and evaluates the morphotectonic activity based on the shape of the watersheds. By measuring and combining these indicators, the tectonic activity stage of the Sirch region was determined by analyzing the watersheds of this region.