Editorial note for the Geodesy and Geodynamics journal special issue:Remote Sens

Crustal deformation and neotectonics are well-understood phenomena that happen almost on every part of the Earth and have some diastrophic effects on the Earth's surface.To understand these effects, Remote Sensing(RS) and (GIS) have sharpened the human ability to learn about the scientific reasons for the Earth's dynamic activities, including active tectonics and surface landform changes in spatially and temporally. With the improved Earth Observatory(EO) techniques, such as Electrical Resistivity Tomography (ERT),Global Navigation Satellite System(GNSS),Ground Penetrating Radar(GPR),Total Electron Content(TEC),Magnetometer,Gravimeter,Engineering seismograph, Time-Domain Electromagnetic (TDEM),Ground Magnetic Resonance (GMR), Broad Band Seismometers(BBS), Strong Motion Accelerograph (SMA), Magnetotellurics (MT)coupled with RS and GIS have immensely revolutionized the crustal deformation and neotectonic studies [1-13].

Researchers worldwide are extensively working on the Earth's dynamism,the crustal deformation activities,and its consequences on the Earth's surface and mankind. The present volume is one of the most special in which research articles were combined from advanced perspectives of crustal deformation and neotectonics using RS and GIS techniques.

The collected articles cover various aspects of active tectonics,applications of geodetic strain and stress variation,morphotectonics,GPS,and PSInSAR based analysis.As is well understood that the space borne RS, with its ability to provide synoptic and repetitive coverage, has emerged as a powerful tool for the assessment and monitoring of the Earth's dynamic activities [14-18]. Therefore, it is expected that the methods and innovations discussed in the special issue will help both scientific and non-scientific communities to develop strategies to address the important issue of Geosciences in a sustainable way.

Among the contributors of this special issue,Kothyari et al.[18]carried out a review study of the Quaternary tectonic history of seismically active intraplate Kachchh Rift Basin(KRB)in western India, to inspect and perceive the association amongst the strain build-up, earthquake provenance, landform evolution, and progression archived by the Quaternary deposits of the KRB, and also emphasized the differences and directions for future research issues. Further, the study suggested that the uplift rates constricted from geomorphic and chronological aspects suggest that the tectonic movements within the Kachchh intraplate region are regulated by the fault segments present. The present tectonic stress field is in accordance with the encompassing tectonic stress field associated with the northward movement of the Indian plate corresponding to the Eurasian plate.Suribabu et al. [19] carried out the geodetic characterization of the active Katrol Hill Fault (KHF) of Central Mainland Kachchh region of western India.The geodetic results highlighted the accumulation of strain up to 22 nano strain/yr and revealed segmented behavior of the KHF in the seismically active Kachchh towards the western part of the Indian plate.

Gunti et al.[20]have studied the state of strain prevalent during the Gorkha earthquake of 2015 in Nepal by using the systematic analysis of pre- and post-seismic GNSS data from 30 continuously operating reference stations (CORS). The co-seismic offsets associated with the Gorkha earthquake have been analyzed in the vicinity of the two earthquake epicenters(Gorkha and Dolakha)and variation in b-value has been estimated,before and after the earthquake using G-R relation. The integrated information using weighted overlay analysis illustrates the earthquake vulnerability in the region and may provide insights into the elastic strain energy balance on the Main Himalayan Thrust (MHT). Joshi et al. [21] used the drainage to tectonics and Persistent Scatterer Interferometry (PSInSAR) technique to derive the deformation in the Bilaspur region of Satluj river basin of north-western Himalaya,India.The study investigates the region's tectonics with the help of drainage signatures and highlights the drainage anomalies due to fault movement.In addition,the study also emphasized that,the intense subsurface activity along the major fault lines caused drainage anomalies in the area using morphometric parameters, which had subtle subsurface activity and can be magnified by the drainage response,and further validated with the generated seismic b-value which also confirms that Bilaspur lies in the cumulative stress zone.

Kumar et al. [22] studied the various aspects of geomorphic indices identified active traces of faults in the Daman Ganga watershed in the western part of India. The study concludes with the relative active tectonics evaluation using geomorphic and drainage indices and also supported by the field evidence, in Dadra and Nagar Haveli, western India. Dumak et al. [23] studied the crustal deformation measurements by the global positioning system(GPS) along the Narmada Son Lineament (NSL) region of western India. The study reveals maximum deformation of western 1.6 mm per year, and the upper bound of the seismic moment(M0) of 2.0 × 1024 dyn/cm, corresponding to an earthquake of about 6.0 magnitude based on the dataset from 2009 to 2016.

Sharma [24] carried out the study regarding the manifestation of the earthquake preparation zone in the ionosphere before the earthquake revealed by GPS -TEC data in the Sonitpur, Assam earthquake, India. The study suggests that the deviation in ionosphere TEC, significantly decrease in TEC concentration before the Sonitpur earthquake, may have resulted from the manifestation of stress development in the crustal rocks.The TEC variations study at different CORS situated at distances from the epicenter showed decreases in TEC values towards the epicenter.The trend in TEC variations was observed within the window of 579 km from the earthquake epicenter,i.e.,very close to the earthquake preparation zone of 565 km.Pearson's correlation coefficient(r)also suggested initial decreases in TEC concentration at CORS that lie within a distance of 565 km,which coincides with the radius of the earthquake preparation zone.Besides this,Hernˊandez-Andrade et al.[25]also carried out a similar kind of work in the Mexico using 65 CORS - GPS stations data.The present study focused on performing a quality check of 10-year of continuous GPS observations considering the values from the International GNSS Service(IGS),the 65 CORS from several networks were utilized to estimate new values that represented the real situation in Mexico. The study also proposed a new approach for estimation of regional values with descriptive statistics of the multipath, signal-to-noise ratio, cycle slips, and integrity with a comprehensive data set. Additionally, an in-depth quality check for the worst and the best CORS were correlated.The signal degradation was proved by performing a long-term time series analysis with GAMIT/GLOBK,which was analyzed and compared with a previous study of crustal deformation in the northeast of Mexico, a seismic active country in the North America.

Chauhan et al.[26]studied the magnetic structure and geomorphic characteristics of neotectonic activity along a strike distance of North Almora Thrust, Kumaun Lesser Himalaya, India, and identified four new faults, on the basis of field study, geomorphic landform and magnetic fabric analysis. These faults are N-S trending Pancheshwar Fault, NE-SW Rameshwer Fault, NNE-SSW trending Kosi Fault, and NNE-SSW trending Gagas Fault (GF). Further, the result revealed that the zone is bound by cross-cutting relation with NAT and these fault zones are comparatively more active than other regions in the Himalayas. Furthermore, the study also suggests that the steep and NW-SE orientation of magnetic foliation within the NAT zone results from NE-SW oriented progressive regional compression. The magnetic foliations represent the unseen internal foliations in the rocks developed due to the preferred alignment of magnetic minerals and can be found through the Anisotropy of magnetic susceptibility (AMS) study. Further, the lowering of anisotropy (Pj) away from the fault zone represents the strain distribution across the NAT zone.

Jadala et al.[27]carried out the integrated study of water vapor during active and break spells of monsoon and its relationship with temperature,precipitation and precipitation efficiency over a tropical site. A preliminary investigation where the GPS measured zenith delays of two years (2014 and 2015) are converted to IWVs using MET data of collocated MBLM and interpolated MET data of IMD, and have been validated with the recent ECMWF Re-Analysis(ERA)91 level data with a satisfactory agreement.However,the measured winds do not show such close agreement with the model data, particularly during the summer months. integrated water vapor (IWV) data are then split into active and break spells of Indian summer monsoon for the two years under study.Further,the diurnal variations of IWV during active and break spells have been studied by applying harmonic analyses. The diurnal, semidiurnal, and terdiurnal components do not show a clear trend with respect to the spells,however,their mean amplitudes during break spells show approximately double amplitudes compared to those during active spells.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgment

The guest editors (AKT, GCT, R, SZ and MK) are immensely thankful to all the reviewers of this Special Issue for timely providing the review/s comments.This Special Issue would remain incomplete without expressing our sincere and deep sense of gratitude to Hongtai Chao, Editorial Council Chairman of Geodesy and Geodynamics, and Dr.Heping Sun, Editor-in-Chief of Geodesy and Geodynamics, for giving us the opportunity to make this special issue. My sincere thanks to editorial office of Geodesy and Geodynamics, for constant support and guidance for the timely completion of this special issue. Our special thanks also to the contributing authors of this special issue,without whom the issue would not be a reality. AKT is also thankful to all the guest editors for consistent and dynamic pursuance to complete the special issue well in time.