Deformation characteristics of the 2016 Mw5.9 Menyuan (China) earthquake by modelling Sentinel-1A and auxiliary data

ABSTRACT

The 2016 M_w5.9 Menyuan earthquake occurred on the Qilian-Haiyuan fault system on the northeastern margin of the Tibetan Plateau. Since the seismogenic source is a blind fault, it is difficult to obtain reliable geometric parameters of the source only from the satellite data. In this paper, we used two aftershock relocation data sets to constrain the seismogenic fault, and obtained two southwest-dipping listric fault models with a strike of about 126° and different dip angles. According to the geological structures, we assumed that the dip is uniformly reduced along the width direction, and modelled the Interferometric Synthetic Aperture Radar (InSAR) data of the Menyuan event using a simulated annealing algorithm to search for the optimal fault dips. The optimal top and bottom dips are about 59° and 1°, respectively. Using the optimal fault model, we obtained the slip distribution and three-dimensional displacement fields for the 2016 M_w5.9 Menyuan earthquake. Sliding occurs mainly on the four sub-faults in the middle of the model, indicating that the rupture zone is relatively small. The displacement fields indicate that the seismogenic source is a thrust fault, and the epicentre experienced a strong northeastward compression deformation.     

Coseismic deformation and source model of the 12 November 2017 MW 7.3 Kermanshah Earthquake (Iran–Iraq border) investigated through DInSAR measurements

A large earthquake with a magnitude of M_W 7.3 struck the border of Iran and Iraq at the province of Kermanshah, Iran. In our study, coseismic deformation and source model of the 12 November 2017 Kermanshah Earthquake are investigated using ALOS-2 ScanSAR and Sentinel-1A/B TOPSAR Differential Interferometric Synthetic Aperture Radar (DInSAR) techniques. Geodetic inversion has been performed to constrain source parameters and invert slip distribution on the fault plane. The optimised source model from joint inversion shows a blind reverse fault with a relatively large right-lateral component, striking 353.5° NNW-SSE and dipping 16.3° NE. The maximum slip is up to 3.8 m at 12–14 km depth and the inferred seismic moment is 1.01 × 10²⁰ Nm, corresponding to M_W 7.3, consistent with seismological solutions. The high-resolution optical images from SuperView-1 satellite suggest that most of the linear surface features mapped by DInSAR measurements are landslides or surface cracks triggered by the earthquake. Coulomb stress changes on the source fault indicating consistency between aftershock distribution and high loaded stress zones. Based on the stress change on neighbouring active faults around this area, the Kermanshah Earthquake has brought two segments of the Zagros Mountain Front Fault (MFF), MFF-1 and MFF-2, 0.5–3.1 MPa and 0.5–1.96 MPa closer to failure, respectively, suggesting the risk of future earthquakes. Recent major aftershocks (M_W≥ 5.0) could probably ease the seismic hazard on MFF-2, but the risk of earthquakes on MFF-2 is still increasing.     

The positive temperature anomaly as detected by Landsat TM data in the eastern Marmara Sea (Turkey): possible link with the 1999 Izmit earthquake

A long (～15 km) and narrow (～4 km) offshore positive temperature anomaly (～1.7° C) is observed in the Landsat Thematic Mapper (TM) thermal infrared (TIR) image acquired the day following the large ?zmit earthquake (Mw 7.4) of 17 August 1999, in eastern Marmara Sea, Turkey. The earthquake was generated along the North Anatolian Fault, which ruptured for about 150 km, and the anomaly formed at the western termination of this rupture. Discussions of this anomaly may develop by processes different than the seismic activity and considerations on fault geometry and sea bathymetry characteristics suggest that the anomaly may result from aftershock activity near the western end of the earthquake fault. The formation of the anomaly requires the addition of a large quantity of hot waters to the sea. The ascent to the sea bottom of fault‐driven hot fluids (seismic pumping) and formation of thermal plumes may be the processes by which the sea surface temperature increased. Recent works and the present study suggest that TIR data analysis may be used as a tool in seismological studies.     

Spatial distribution of the surface rupture zone associated with the 2001 Ms 8.1 Central Kunlun earthquake,northern Tibet,revealed by satellite remote sensing data

The Ms 8.1 Central Kunlun earthquake occurred on 14 November 2001 in northern Tibet, China. Landsat Enhanced Thematic Mapper (ETM) and Thematic Mapper (TM), Système Probatoire de l'Observation de la Terre (SPOT) High Resolution Visible (HRV) panchromatic, and Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) visible and near-infrared (VNIR) images before and after the earthquake are compared to detect the spatial distribution of the surface rupture zone. A surface rupture zone at least 400 km long produced by this event can be accurately identified from satellite sensor images. It is the longest surface rupture zone among the coseismic rupture zones ever reported worldwide. In spatial terms, the surface rupture zone consists of two segments. The eastern segment extends about 350 km striking N75°-85°W (between 91°07' E and 94°55' E), and the western segment bends south-west extending more than 70 km to west of Sun Lake with a strike of N50°E-N70°W (west of 91°07' E). Analyses of satellite sensor images are well consistent with ground data obtained from the field survey. High spatial resolution satellite remote sensing techniques, therefore, provide a rapid and powerful tool to detect the co-seismic surface rupture in the remote and high mountainous Tibet area.     

Measurement of the left‐lateral displacement of Ms 8.1 Kunlun earthquake on 14 November 2001 using Landsat‐7 ETM+ imagery

An imageodesy study has been carried out, using pre‐ and post‐event Landsat‐7 Enhanced Thematic Mapper Plus (ETM+) images, to reveal regional co‐seismic displacement caused by the Ms 8.1 Kunlun earthquake in November 2001. The two Landsat scenes, Kusai Lake and Buka Daban, cover an area of some 57 600 km² (320 km W–E and about 180 km N–S), which includes most of the fault rupture zone. The co‐seismic displacement measured in the Kusai Lake scene shows that the average left‐lateral shift along the Kunlun fault is 4.8 m (ranging from 1.5 to 8.1 m) and the maximum shift appears west of the Kusai Lake. The splayed nature of the fault to the west of Buka Daban, where the fault splits into three branches, causes the displacement pattern to become complicated. Here the average left‐lateral shift, between the south side of the southern branch and the north side of the northern branch, is 4.6 m (ranging from 1.0 to 8.2 m). Our results also illustrate that the south side of the fault is the ‘active’ block, moving significantly in an east–south‐easterly direction, relative to the largely ‘stable’ northern block.     

Unique atmospheric wave: precursor to the 26 January 2001 Bhuj,India, earthquake

A unique atmospheric wave was recorded by a monostatic sound detection and ranging (sodar) system operating at Vapi, India (20.37° N, 72.90° E), on 25 January 2001 prior to the Bhuj, India, earthquake that jolted India on 26 January 2001. This precursory wave was the largest amplitude (480 m) and lowest frequency wave (70.02 μHz) ever recorded at 25 sodar operational sites in India/Maitri, Antarctica, in the past 30 years. It appears to be an Acoustic Gravity Wave (AGW) propagating in the lower atmosphere, and this precursory signature may support the hypothesis of AGW generation prior to a major earthquake.     

Mapping active fault associated with the 2003 Mw 6.6 Bam (SE Iran) earthquake with ASTER 3D images

Satellite images reveal the geomorphology and geometry of an active fault associated with an earthquake that caused over 40,000 deaths in southeast Iran. This earthquake, of moment magnitude (Mw) 6.6, occurred at 01:56:52 (UTC) on December 26, 2003 near the towns of Bam and Baravat. An active fault that ruptured during the earthquake can be seen on three-dimensional (3D) pre- and post-earthquake images generated from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) visible and near infrared (VNIR) data. The interpretation and analysis of satellite images suggest that a dextral fault extends for 65 km through the Bam-Baravat region. It strikes north-northwest and steps leftward at a segment boundary between two towns. Transpressional stress at this step-over (bend) probably triggered the 2003 earthquake rupture, as suggested also by source mechanism solution of the Bam earthquake and by landforms observed in the field. In the past 2000 years, Bam has had no earthquake as destructive as the one in 2003. The potential for this catastrophe could have been identified through a combination of satellite remote sensing technique and field reconnaissance.     

Seasonal and temporal study of the northwest African upwelling system

The upwelling index (UI) obtained from sea surface temperature (SST) images for the period 1987–2006 and remote sensing wind stress were used to analyse the features of the coastal upwelling region off northwest Africa. The seasonal distribution shows a persistent upwelling throughout the year from 20° N to 33° N, seasonal behaviour from 12° N to south of 20° N, and an almost total lack of upwelling throughout the year from 5° N to 12° N. The major centres of active upwelling are located around Cape Ghir, Cape Juby and Cape Blanc. The UI shows an intensification of the upwelling system off northwest Africa during the 20-year period while the alongshore wind stress remains almost stable. During this period, upwelled waters off Cape Blanc have increased their offshore spreading.     

The use of Landsat Thematic Mapper imagery for analysing lithology and structure of Korucu-Du[ggrave] la area in western Turkey

The Korucu-Dugla study area ( 225km² ) located in western Turkey was selected for the application of Landsat Thematic Mapper ( TM) data to geological studies. A wide variety of image processing techniques including; principal component analysis ( PC) intensity-saturation-hue transformation ( ISH), TM band ratios, and edge enhancement were applied to discriminate the lithologies and structure as well as associated areas of hydrothermal alteration. Colour composites of PCI, 2 and 3, always encoded red, green and blue respectively, PC4, 3 and 2, ISH transformation of TM bands 1, 3 and 5, were found most suitable for lithology and boundary discrimination in the area. A colour composite of 3/ 1, 4/ 3, and 5/ / 7 ratio images was prepared to separate altered areas. Altered areas, which have potential for mineralization, were mapped on the constructed geological map. A number of previously unmapped faults and subunits of the formations were discriminated successfully. A lineament map and rose diagram were prepared using high-pass Laplacian niters. The rose diagram showed a good correspondence with the strike of previously mapped earthquake fault breaks. The linear features of the area have dominant directions at N 30-40^° E and N 60-80^° E. Alteration and mineralization in the Korucu-Dugla area are mostly controlled by NNE and EW trending structures.     

Analysis of space- and ground-based parameters prior to an earthquake on 12 December 2009

The present study includes observations of anomalies at ionospheric and ground levels using data from global positioning system (GPS)-based total electron content (TEC), ionospheric electron density by Detection of Electromagnetic Emissions Transmitted from Earthquake Regions (DEMETER), and ground-based ultra-low-frequency (ULF) emission prior to an earthquake that occurred on 12 December 2009. The analysis of the data from these three different techniques show relations with preseismic activities. The GPS-based TEC showed enhancement three days prior to the day of the earthquake. On converting the satellite azimuth into latitude and longitude, a large number of passes giving anomalous TEC values were observed covering a zone 17–23° N and 70–74° E (i.e. around the epicentre). Electron density and temperature as measured by DEMETER also show enhancement of the tracks around the epicentre one day prior to the earthquake. For ground-based ULF emission, we used different analysis techniques for the detection of abnormal changes in ULF emission before the earthquake. We observed changes in different parameters such as polarization ratio and fractal dimension. Clear enhancement is observed for polarization parameters (Z/X, Z/Y) and fractal analysis (for the Z component). The results provide useful information in acquiring data prior to earthquakes.     

Effects of zonal wind on stratospheric ozone variations over Nigeria

The effects of zonal wind on stratospheric ozone (O₃) variation over Nigeria have been studied. The areas covered in this study include: Maiduguri (11.83° N, 13.15° E), Ikeja (6.45° N, 3.40° E), Port-Harcourt (4.75° N, 7.00° E), Calabar (4.95° N, 8.33° E), Makurdi (7.73° N, 8.54° E), Ilorin (8.50° N, 4.55° E), Akure (7.17° N, 5.08° E), Yola (9.23° N, 12.46° E), Minna (9.61° N, 6.56° E), Jos (9.93° N, 8.88° E), Kano (12.00° N, 8.52° E), and Enugu (6.45° N, 7.51° E), from 1986 to 2008. Zonal wind data was computed from the iso-velocity map employing Matrix Laboratory (MATLAB) software. The mean monthly variations of atmospheric angular momentum (AAM) and length of day (LOD) at pressure levels of 20, 30, and 50 mbar in the atmosphere mostly depict a trend of maximum amplitude between April and September, and minimum amplitude between December and March. The trend observed in seasonal variation of column ozone data in the low latitude had maximum amount from May through August and minimum values from December through February. The mean monthly maximum O₃ concentrations was found to be 284.70 DU occurring at Kano (12.00° N, 8.52° E) in May 1989 while an average monthly minimum O₃ concentration was found to be 235.60 DU occurring at Port-Harcourt and Calabar (4.75° N, 7.00° E and 4.95° N, 8.33° E, respectively) in January 1998. It has been established in this study that the variation in LOD caused by AAM mostly transfer O₃ by means of zonal wind from the upper troposphere to the lower stratosphere in the stations under study. The strong effect of the pressure levels of the atmosphere on O₃ variation could be attributed to its effect on the AAM and LOD. Variation in the LOD is significant in the tropics, suggesting that the effects of the extra-tropical suction pump action are not the only driver responsible for O₃ transportation from the tropics to extra-tropical zones. Analyses show a relationship with strong correlation between rainfall intensities and total ozone throughout the year under study. For instance, the obtained value of r ranges between 0.676 and 0.957 and p-value <0.05. This most likely indicates that the phenomenon could probably contribute to total ozone variations in Nigeria. Consequently, these findings lead to a deduction that weather pattern alteration observed due to these changes could lead to climate change.     

The Al Hoceima (Morocco) earthquake of 24 February 2004, analysis and interpretation of data from ENVISAT ASAR and SPOT5 validated by ground-based observations

The magnitude M_w = 6.3 earthquake in Al Hoceima, Morocco of 24 February, 2004 occurred in the active plate boundary accommodating the oblique convergence between Africa and Eurasia. Three different sets of estimates of its source parameters have already been published. We try to resolve the discrepancies between them by using additional data including two remote sensing satellite systems (ENVISAT and SPOT5). Using a model with a dislocation in an elastic half-space, we constrain the source parameters. The hypothesis of two subevents on distinct faults as inferred from seismological inversions is confirmed here by adopting a cross-fault mechanism. The rupture began on a left-lateral strike-slip fault striking at N10° azimuth with 90 cm of horizontal slip and then transferred to a right-lateral strike-slip fault striking at N312° azimuth with 85 cm of horizontal slip. The first fault is at 500 m depth from the free surface and the second fault is at 3 km depth. This model is consistent with ground-based observations, including GPS, seismology, and mapped surface fissures. The pair of faults activated in 2004 appears to constitute part of a complex seismogenic structure striking NNE-SSW that separates the Rif tectonic blocks.     

Neural networks to predict earthquakes in Chile

A new earthquake prediction system is presented in this work. This method, based on the application of artificial neural networks, has been used to predict earthquakes in Chile, one of the countries with larger seismic activity. The input values are related to the b-value, the Bath's law, and the Omori–Utsu's law, parameters that are strongly correlated with seismicity, as shown in solid previous works. Two kind of prediction are provided in this study: The probability that an earthquake of magnitude larger than a threshold value happens, and the probability that an earthquake of a limited magnitude interval might occur, both during the next five days in the areas analyzed. For the four Chile's seismic regions examined, with epicenters placed on meshes with dimensions varying from 0.5° × 0.5° to 1° × 1°, a prototype of neuronal network is presented. The prototypes predict an earthquake every time the probability of an earthquake of magnitude larger than a threshold is sufficiently high. The threshold values have been adjusted with the aim of obtaining as few false positives as possible. The accuracy of the method has been assessed in retrospective experiments by means of statistical tests and compared with well-known machine learning classifiers. The high success rate achieved supports the suitability of applying soft computing in this field and poses new challenges to be addressed.     

Long-term trends of total ozone content over mid-latitudes of the Northern Hemisphere

Dynamic climatic normals and long-term trends of total ozone in the mid-latitudes of the Northern hemisphere (30°N–60°N) have been determined using data from satellite observations for the period of 1978–2017. The annual course of total ozone is shown as changing over the various regions during the period of observations. The specific features of alteration in the state of the ozone layer are discussed depending on latitude and longitude. Thus, a general increase in total ozone in winter, an increase in spring (with the exception of the northern latitudes of Europe, Asia, and Pacific), and a continuing decrease in summer (with the exception of the northern latitudes of America) during the last 17 years is revealed. The long-term trends of total ozone for different regions and latitude zones (30°N–40°N, 40°N–50°N, and 50°N–60°N) are given depending on season.     

Cloud anomaly before Iran earthquake

In the 1980s Russian scientists found a thermal anomaly before an earthquake and abnormal cloud above an active fault. In the following 20 years, thermal anomalies were widely studied, however abnormal cloud was seldom reported. Here geostationary satellite sensor data was used to study the abnormal cloud above the Iran active fault. The linear traces with high temperature in thick clouds spread along the main tectonic structures. Sixty‐nine days later a M6.3 earthquake occurred close to the abnormal clouds. The same clouds appeared on 25 December 2005 and 64 days later a M6.0 earthquake occurred. In these two cases, the abnormal clouds indicated the rough area of the future epicentre. If geophysical measurement data, satellite thermal data and abnormal cloud data are combined, it is possible that it will contribute to earthquake studies.     

Regional assessment of geohazard recovery eight years after the Mw7.9 Wenchuan earthquake: a remote-sensing investigation of the Beichuan region

The earthquake of 12 May 2008 in Wenchuan County, Sichuan Province, China, devastated the entire Beichuan region. Sitting at the intersection of the Yingxiu-Beichuan and Pengguan faults, the region experienced seismic intensities of VIII–XI on the Liedu scale. High seismic intensity combined with inherent geomorphological and climatic susceptibility to slope failure resulted in widespread co-seismic geohazards (slope failures of various types), which decimated the region. The seismic characteristics of the Wenchuan earthquake and the co-seismic geohazard distribution in relation to various conditioning factors have previously been examined in depth. However, there has been a lack of regional assessment of temporal and spatial recovery from co-seismic geohazards. Triggered by the authors’ field observation of rapid recovery, this study presents a temporal series of geohazard maps, produced by manual interpretation of satellite imagery, to present an initial assessment of changes in geohazard occurrence in the Beichuan region since the Wenchuan earthquake. In particular, landscape recovery at the co-seismic geohazard sites, as indicated by re-vegetation, is analysed based on temporal/spatial characteristics of geohazard distribution, in relation to co-seismic deformation, distance from the rupture zone and slope angle. Eight years after the Wenchuan earthquake, the overall recovery stands at 65.48%, with approximately uniform annual rates of recovery at 13.45% a year between 2009 and 2011 and 10.56% a year between 2012 and 2016. Whilst co-seismic geohazards are concentrated on the hanging wall of the seismic fault, landscape recovery is more significant in the very highly deformed zone than in other areas. Recovery has been the greatest on slopes of <50^° and peaks on 40^°–50^° slopes, where the area occupied by co-seismic geohazards was the largest. The block-slides and rock topples, which characterize high angle slopes, show much slower recovery, possibly due to greater instability and the lack of soil to support re-vegetation.     

Analysis of GPS-based TEC and electron density by the DEMETER satellite before the Sumatra earthquake on 30 September 2009

An analysis of ionospheric total electron content (TEC) variations obtained using Global Positioning System (GPS) measurements and electron density observations by the Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions (DEMETER)/ISL before the Sumatra earthquake (magnitude 7.6) on 30 September 2009 is presented. The data used are global TEC maps created in the IONEX format to estimate the spatial scale of ionospheric irregularities associated with this earthquake and DEMETER/ISL observations to analyse plasma parameter changes during earthquakes. This study for the first time integrates ground-based GPS receiver and space-based DEMETER/ISL observations to probe seismo-ionospheric anomalies before a large earthquake. The pre-seismic behaviour of the TEC was detected within a few days before the main event. The anomaly appeared as local TEC enhancement in the vicinity of the forthcoming earthquake epicentre. These structures were generated in the ionosphere at a similar local time at 1, 3 and 5 days prior to the main shock. The equatorial anomaly trough moved northwards (5°) on the earthquake day and 7.5° southwards the next day. The results demonstrate that both enhanced and reduced anomalies in the ionospheric electron density appeared before the Sumatra earthquake. The results from International GNSS Service (IGS) GPS data demonstrate that TEC variations can be used to detect seismo-ionospheric signatures.     

Co‐seismic ruptures found up to 60 km south of the Kunlun fault after 14 November 2001, Ms 8.1, Kokoxili earthquake using Landsat‐7 ETM+ imagery

A systematic visual interpretation of pre‐ and post‐earthquake Landsat‐7 ETM+ imagery of the 14 November, Ms 8.1 Kokoxili earthquake has revealed significant post‐earthquake lineaments in the region south of the Kunlun fault, which we interpret as co‐seismic surface ruptures related to the event. This previously unreported surface rupturing is located in two broad swathes ～20 and ～60 km south of the main Kunlun fault. Pre‐existing lineaments and subtle tectonic geomorphologic features associated with these ruptures suggest that earthquake‐triggered displacement occurred along pre‐existing faults.     

Co‐seismic surface ruptures produced by the 2005 Pakistan M w7.6 earthquake in the Muzaffarabad area,revealed by QuickBird imagery data

High‐resolution QuickBird imagery data have been used to analyse and detect the co‐seismic surface ruptures produced by the 2005 Pakistan M _w7.6 earthquake in the Muzaffarabad area. The analytical results and interpretations of the QuickBird images reveal that the co‐seismic surface ruptures are mostly concentrated on the pre‐existing active faults striking northwest–southeast. Most of co‐seismic surface ruptures show a deformation feature of compressional cracks having a right‐stepping echelon geometric pattern. Individual cracks vary from metre order to 1‐km in length, generally 10 to 100 m. In the northern Muzaffarabad city, an east–west striking co‐seismic surface zone of ～1 km length occurred in the jog area between two northwest–southeast striking surface rupture zones. A strong damage zone along which all buildings completely collapsed is concentrated in a deformation zone of ～60 m wide on the uplift side of the east–west striking surface rupture zone. Large‐scale landslides caused by strong ground motion are mostly constricted on the uplift side along the co‐seismic surface rupture zones. The deformation features and spatial distribution patterns of the co‐seismic surface ruptures and the ground motion direction indicate that the co‐seismic fault that triggered the 2005 Pakistan M _w 7.6 earthquake is a thrust fault with a right‐lateral slip component.     

On a 16° N chlorophyll plume along the east coast of India

The plume rich with chlorophyll‐a concentration (>0.3 mg/l) observed on 22 March 2003 along the 16° N in the western Bay of Bengal off the Krishna–Godavari river delta was studied. Relatively high sea surface temperature (>30° C) observed in the plume area indicated their origin in the coastal waters. The bloomy plume was found spreading 400 to 500 km offshore in the form of an offshore jet extending as far as 86° E in the Bay of Bengal. An offshore flow was observed with geostrophic velocity exceeding 50 cm/s with a cyclonic eddy on its north around 17° N, 82° E and an anti‐cyclonic eddy around 14° N, 83° E to its south. The hydrographic data of the area were studied with the observations made by GTS data buoy indicated coastal upwelling. Similar plumes were also observed during the years 2004 and 2005.