Seismicity of region around dams in North West India

The collision of Indian and Eurasian continents caused large scale deformation and high seismicityof vast areas of both continents in the geological history. The North-West portion of the Himalayan arc which is lyingunder the rupture zones of Kangra earthquake of 1905, Uttarkashi earthquake of 1991 and Chamoli earthquake in 1999,has experienced many earthquakes of magnitude 6 and above. The region of North-West India between 30.0º - 35.0ºNorth and 73.0º - 79.0º East is, therefore, under intense investigations by various scientists since the origin of theHimalayas. India Meteorological Department had opened thirteen seismic observatories in early sixties for monitoringof earthquake activities in and around Bhakra, Pong, Pandoh dams in Punjab / Himachal Pradesh and Salal dam inJ&K on specific demand of the dam authorities. These observatories have recorded the earthquakes occurred in thisregion having magnitude even less than 2. The data collected for the last two decades is very useful for the scientiststo investigate seismicity and tectonics of the Himalayas. The present study could locate the regions which areseismically most active and also the region of seismic gap. Thus present study confirms association of seismic activityin the region with two major fault systems called Main Boundary Thrust (MBT) and Main Central Thrust (MCT).Comparative seismic activity within 100 km from each dam, reveal that most active region was around Pong followed byPandoh, Bhakra and Salal dams. The temporal variation of b-values for the whole period also shows that low b-valueanomalies are usually followed by large earthquakes of M > 5.5. No definite conclusions could be drawn with regard tothe relationship between the observed seismic activity around the dam sites with the corresponding water levelfluctuations in the reservoirs.

Complex Slip Distribution of the 2021 Mw 7.4 Maduo, China, Earthquake: An Event Occurring on the Slowly Slipping Fault

The 21 May 2021 Maduo earthquake occurred on the Kunlun Mountain Pass–Jiangcuo fault (KMPJF), a seismogenic fault with no documented large earthquakes. To probe its kinematics, we first estimate the slip rates of the KMPJF and Tuosuo Lake segment (TLS, ∼75 km north of the KMPJF) of the East Kunlun fault (EKLF) based on the secular Global Positioning System (GPS) data using the Markov chain Monte Carlo method. Our model reveals that the slip rates of the KMPJF and TLS are 1.7 ± 0.8 and 7.1 ± 0.3 mm/yr, respectively. Then, we invert high-resolution GPS and Interferometric Synthetic Aperture Radar observations to decipher the fault geometry and detailed coseismic slip distribution associated with the Maduo earthquake. The geometry of the KMPFJ significantly varies along strike, composed of five fault subsegments. The most slip is accommodated by two steeply dipping fault segments, with the patch of large sinistral slip concentrated in the shallow depth on a simple straight structure. The released seismic moment is ∼1.5×1020 N·m, equivalent to an Mw 7.39 event, with a peak slip of ∼9.3 m. Combining the average coseismic slip and slip rate of the main fault, an earthquake recurrence period of ∼1250−400+1120 yr is estimated. The Maduo earthquake reminds us to reevaluate the potential of seismic gaps where slip rates are low. Based on our calculated Coulomb failure stress, the Maduo earthquake imposes positive stress on the Maqin–Maqu segment of the EKLF, a long-recognized seismic gap, implying that it may accelerate the occurrence of the next major event in this region.

Ground-penetrating radar signature of Quaternary faulting: a study from the Mt. Pollino region, southern Apennines, Italy

With the aim of unveiling evidence of Late Quaternary faulting, a series of ground-penetrating radar (GPR) profiles were acquired across the southern portion of the Fosso della Valle–Campotenese normal fault (VCT), located at the Campotenese continental basin (Mt. Pollino region) in the southern Apennines active extensional belt (Italy). A set of 49 GPR profiles, traced nearly perpendicular to this normal fault, was acquired using 300 and 500 MHz antennas and carefully processed through a customized workflow. The data interpretation allowed us to reconstruct a pseudo-3D model depicting the boundary between the Mesozoic bedrock and the sedimentary fill of the basin, which were in close proximity to the fault. Once the GPR signature of faulting was reviewed and defined, we interpret near-surface alluvial and colluvial sediments dislocated by a set of conjugate (W- and E-dipping) discontinuities that penetrate inside the underlying Triassic dolostones. Close to the contact between the continental deposits and the bedrock, some buried scarps which offset wedge-shaped deposits are interpreted as coseismic ruptures, subsequently sealed by later deposits. Our pseudo-3D GPR dataset represented a good trade-off between a dense 3D-GPR volume and conventional 2D data, which normally requires a higher degree of subjectivity during the interpretation. We have thus reconstructed a reliable subsurface fault pattern, discriminating master faults and a series of secondary splays. This contribution better characterizes active Quaternary faults in an area which falls within the Pollino seismic gap and is considered prone to severe surface faulting. Our results encourage further research at the study site, whilst we also recommend our workflow for similar regions characterized by high seismic hazard and scarcity of near-surface geophysical data.

Evacuation route during a disaster with health protocol in the new normal era

The southern coast of Java Island, one of which is Sumbermanjing Wetan District, Malang Regency, is considered prone to the geological disaster tsunami. Sumbermanjing Wetan District is directly adjacent to the Indian Ocean, a seismic gap zone that produces geological processes and high-intensity seismic activity that can trigger tsunami waves. On June 13, 2021, the COVID-19 outbreak in Sumbermanjing Wetan District recorded 90 suspected cases (two were hospitalized and the other 88 were self-isolating at home), and 38 were confirmed positive for COVID-19 (34 recovered and 4 died). This research focuses on evacuation plans for coastal areas from the threat of a tsunami during the pandemic and the new normal era. The sub-variables for determining the shelters include building area, type of building, ease of access, building construction, and capacity. The sub-variables for determining the evacuation route include road class, pavement type, and road width. Meanwhile, the sub-variables for implementing health protocols in the new normal era are maintaining distance, wearing masks, washing hands, special treatment for symptomatic refugees, and implementing other health protocols. The implementation of health protocols in evacuation activities will bring an impact on the reduction of the available shelter’s capacity. The study results indicate the need for additional new shelters to implement health protocols in the new normal era. With this addition, it will impact the travel time from the residential areas at risk of tsunami impacts to the shelters. One of the reasons is that the closest shelter to the residential area is already full of refugees, so the refugees have to move and evacuate to the other shelters that can still accommodate them.

Parametric Characterization and Analysis of Pounding Behavior Adjacent Multi-Storied Buildings of Varying Heights

Many past earthquake studies show that during strong vibrations, the adjacent building structures which are closely spaced to each other are vulnerable to severe damage when the adjacent buildings are not at an adequate distance to accommodate their relative displacements. The primary goal of this research is to find out the minimum separation gap between buildings of varying height at the same floor-to-floor height level. SAP 2000 software is used to analyze the structural behavior of building during the earthquake.Three building models are taken for the study, one is six floors (G+6) and another two are nine floors (G+9), and twelve floors (G+12) respectively. Six floors (G+6)& twelve floors (G+12) structures have the same floor to floor height and plan and same beam and column size (equal stiffness) and G+9 buildings have floor to floor height are same but different beam and column sizes (different stiffness). The linear dynamic (RSA) analysis method is used to calculate the response (Displacement, frequency at fundamental time, Base Shear) of the structure at different floors levels. Response (top story displacements) calculated from the response spectrum is compared with the provisions of seismic gap per story height given in IS 4326: 2005.

Crustal velocity and interseismic strain-rate on possible zones for large earthquakes in the Garhwal–Kumaun Himalaya

The possibility of a major earthquake like 2015 Gorkha–Nepal or even greater is anticipated in the Garhwal–Kumaun region in the Central Seismic Gap of the NW Himalaya. The interseismic strain-rate from GPS derived crustal velocities show multifaceted strain-rate pattern in the region and are classified into four different strain-rate zones. Besides compressional, we identified two NE–SW orienting low strain rate (~ 20 nstrain/a) zones; namely, the Ramganga-Baijro and the Nainital-Almora, where large earthquakes can occur. These zones have surface locking widths of ~ 72 and ~ 75 km respectively from the Frontal to the Outer Lesser Himalaya, where no significant surface rupture and associated large earthquakes were observed for the last 100 years. However, strain reducing extensional deformation zone that appears sandwiched between the low strain-rate zones pose uncertainties on the occurences of large earthquakes in the locked zone. Nevertheless, such zone acts as a conduit to transfer strain from the compressional zone (> 100 nstrain/a) to the deforming frontal active fault systems. We also observed a curvilinear surface strain-rate pattern in the Chamoli cluster and explained how asymmetric crustal accommodation processes at the northwest and the southeast edges of the Almora Klippe, cause clockwise rotational couple on the upper crust moving over the MHT.

Interaction Between Historical Earthquakes and the 2021 Mw7.4 Maduo Event and Their Impacts on the Seismic Gap Areas Along the East Kunlun Fault

On May 21, 2021 (UTC time), a Mw7.4 earthquake struck Maduo County, Qinghai Province, China. The rupture of this typical strike-slip event and its aftershocks along the Kunlun-Jiangcuo fault (JCF) propagated approximately 170 km from the epicenter. In this study, we calculated the coseismic and postseismic Coulomb stress changes induced by 14 historical earthquakes and investigated their impacts on the 2021 Maduo source area. We found that the JCF is in the stress shadow of these historical events with a combined ΔCFS range of approximately -0.4 to -0.2 MPa. Since the seismogenic fault of the 1937 event is nearly parallel and close to the JCF, the rupture of the 1937 event had the greatest inhibitory effect on Maduo source area. We hypothesize that the actual loading rate at the depth of the seismogenic layer in the Maduo source area is much higher than the simulated value (0.3 kPa/a). Consequently, the Maduo earthquake still occurred despite the considerable delaying effect of these historical earthquakes (especially the 1937 event). Our findings also indicate that the tectonic stress in the eastern Bayanhar block is still rapidly accumulating and adjusting. Our investigation further reveals the enhanced stress induced by the historical and Maduo events with ΔCFS values of approximately 30~300 kPa and 50~300 kPa on the XDS and the eastern end of the EKF, respectively, not only on the MMS but also at the eastern end of each branch segment of the EKF. Hence, considering the accumulation of tectonic stress, we suggest that the seismic hazard in these two regions has been promoted.

Ring-shaped seismicity structures, being formed in the Alaska region: Justi-fied prediction of the place and magnitude of the Simeonof earthquake of July 22, 2020 (Mw 7.8)

We have been studying some seismicity characteristics connected with Simeonof earthquake of July 22, 2020 (Mw 7.8) in the area of Shumagin seismic gap, located in the region of South Alaska. 8 years before this event, the authors picked up here ring-shaped seismicity structure. Using characteristics of this structure we made a conclusion on preparation for large earth-quake (Mw~8), similarly to many events in subduction zones. We used data on threshold magnitude and size of the ring structure, and earlier obtained dependences of these parame-ters on magnitudes of main events for the subduction zones in the Eastern Pacific. Accumula-tion of new seismicity data prior to 2020/07/22 allowed us to specify the source location and magnitude of the Simeonof earthquake: Mw=7.9±0.3. It was shown that after this event new ring structures continued to form, which can correspond to preparation for larger earthquake: Mw=8.2±0.2. Geodynamical processes, which lead to formation of the ring structures, are discussing.

Hydro-torrential hazard vs. anthropogenic activities along the Seti valley, Kaski, Nepal: Assessment and recommendations from a risk perspective

The Seti River originates from the Annapurna Massif in the Higher Himalaya of Nepal and flows through the Pokhara valley in the Lesser Himalaya. The Seti River witnessed a disastrous flash flood on May 5th, 2012 causing the death of 72 people, obliterating dozens of homes and damaging infrastructures worth millions of dollars. Despite the 2012 flood event and several warnings by scientists for more yet bigger scale future floods in the Seti valley, fluvial risk is being aggravated by anthropogenic activities such as unplanned human settlement, encroachment of riverbanks, haphazard construction of road, drinking water, and hydropower projects in potential flood hazard areas in addition to the increased impacts of climate change on geological and hydro-metrological hazards as in other parts of Hindu Kush Himalayan Range. Covering some 40-km distance from the Seti headwater (Sabche Cirque) down to Pokhara city, the study is carried out based on hydro-geomorphological mapping, analysis of land-use and land-cover change, hydrological analysis including HEC-RAS modelling, historical archives, and interviews with local people. The study shows a significant change on the land use and land cover of the Seti catchment, mainly the urban/built-up area, which is increased by 405% in 24 years period (1996 to 2020) and by 47% in 7 years period (2013 to 2020). Further the study reveals that anthropogenic activities along the Seti valley have increased fluvial risk and are likely to invite more disasters. From the HEC-RAS analysis, two motor bridges built over Seti River were found to have insufficient freeboard to safely pass the highest flood discharge for 100 years return-period. Instead of relocating people to safer places, the government and local authorities rather seem to have encouraged people to live in the floodplain by providing basic amenities such as drinking water, electricity and access road. Given the context of climate change and Pokhara valley and the Seti catchment being in a high-seismic gap zone, there is a strong possibility of similar flood to the scale of 2012 or even greater in Seti River. Though the fluvial risk can be managed in a sustainable way through the application of functional space concept, i.e., by allowing more space (freedom) for rivers, this economic and environment friendly approach of the fluvial risk management has not been implemented yet in the Seti valley nor in Nepal. Rather the encroachment of floodplains by anthropogenic activities along the Seti valley is on an increasing trend. Many settlements and infrastructures along the valley have been identified vulnerable to hydro-torrential hazards, therefore it is utmost necessity to implement functional space river concept, land use and land plan policy, early warning system and public awareness education in order to mitigate and manage the future impact of fluvial hazards along the Seti valley.

Locating the Italian Radioactive Waste Repository: Issues and Perplexities Arisen from Open Data-Based Analyses about the TO-10 Site (NW Italy)

Recently, Italy has started the procedure for the selection of suitable sites for hosting the National Repository for Low-Medium Activity Radioactive Wastes. Sogin spa, a public company, taking into account the criteria of the ISPRA Technical Guide no. 29, solicited by the EU Directive 2011/70/Euratom, has presented the CNAPI (National Map of the Potentially Suitable Areas) which has become operative since 5 January 2021. Sixty-seven sites were identified in Italy as potentially suitable for hosting the repository. Some criticalities immediately appeared concerning the properness of the selection. An analysis was, therefore, achieved to explore part of the rationales underlying the adopted procedure. A paradigmatic site, namely the TO-10 one (NW Italy), was chosen for the analysis, which highlighted significant anomalies affecting both the procedure rationales and its results. Since the selection process majorly relies on geographical data, attention was particularly paid on the role of official data from open archives. With reference to the most updated and detailed ones, we demonstrated that the Sogin procedure suffers from several critical points. In particular, with reference to the TO-10 site, we found that it cannot be absolutely considered to be suitable for hosting the National Deposit. In fact, it proved to match several exclusion criteria included in the ISPRA Technical Guide n. 29. These include: the potentially high “seismic risk” due to a “seismic gap” and complex tectonics associated with uplift (up to 1–1.5 mm/y); a highly vulnerable and extremely superficial groundwater table; a high permeability (10−2–10−3 m/s) of the cover sedimentary units; not proper buffer zones around local settlements. In spite of the local specificity of the analysis, results concerning procedure weaknesses are general. Consequently, we expect that they can be a stimulus for Sogin to more properly face the next steps of the selection procedure.