Coseismic Deformation Research Articles

Coseismic deformation of the 2020 Yutian MW 6.4 earthquake from Sentinel-1A and the slip inversion

A remarkable earthquake struck Yutian, China on June 26th, 2020. Here, we use Sentinel-1 images to investigate the deformation induced by this event. We invert the InSAR observations using a two-step approach: a nonlinear inversion to constrain fault geometries with uniform slip based on the rectangular plane dislocation in an elastic half-space, followed by a linear inversion to retrieve the slip distribution on the fault plane. The results show that the maximum LOS displacement is 22.6 ​cm, and the fault accessed to the ruptured characteristics of normal faults with the minor left-lateral strike-slip component. The fault model indicates a 210° strike. The main rupture zone concentrates in the depth of 5–15 ​km, and the fault slip peaks at 0.89 ​m at the depth of 9 ​km. Then, we calculate the variation of the static Coulomb stress based on the optimal fault model, the results suggest that the Coulomb stress of the Altyn Tagh fault and other neighboring faults has increased and more attention should be paid to possible seismic risks.

Transient Deformation and Stress Patterns Induced by the 2010 Maule Earthquake in the Illapel Segment

Evaluating the transfer of stresses from megathrust earthquakes to adjacent segments is fundamental to assess seismic hazard. Here, we use a 3D forward model as well as GPS and seismic data to investigate the transient deformation and Coulomb Failure Stresses (CFS) changes induced by the 2010 Maule earthquake in its northern segment, where the Mw 8.3 Illapel earthquake occurred in 2015. The 3D model incorporates the coseismically instantaneous, elastic response, and time-dependent afterslip and viscoelastic relaxation processes in the postseismic period. We particularly examine the impact of linear and power-law rheology on the resulting postseismic deformation and CFS changes that may have triggered the Illapel earthquake. At the Illapel hypocenter, our model results in CFS changes of ∼0.06 bar due to the coseismic and postseismic deformation, where the coseismic deformation accounts for ∼85% of the total CFS changes. This is below the assumed triggering threshold of 0.1 bar and, compared to the annual loading rate of the plate interface, represents a clock advance of approximately only 2 months. However, we find that sixteen events with Mw ≥ 5 in the southern region occurred in regions of CFS changes > 0.1 bar, indicating a potential triggering by the Maule event. Interestingly, while the power-law rheology model increases the positive coseismic CFS changes, the linear rheology reduces them. This is due to the opposite polarity of the postseismic displacements resulting from the rheology model choice. The power-law rheology model generates surface displacements that fit better to the GPS-observed landward displacement pattern.

Sentinel-1 InSAR observations of co- and post-seismic deformation mechanisms of the 2016 Mw 5.9 Menyuan Earthquake, Northwestern China

On January 21, 2016, a Mw 5.9 earthquake occurred in Menyuan, Qinghai Province, in northwestern China, which is an earthquake-prone region located along the northeastern margin of the Tibetan Plateau. However, the source parameters, deformation mechanism, especially the influence of this earthquake on the surrounding regions and on post-seismic deformation, remains poorly understood. In this study, Sentinel-1 images from ascending and descending tracks were used to investigate the co- and post-seismic deformation fields. Uniform and distributed slip models were used to determine the source parameters. Finally, the co- and post-earthquake two-dimensional (2D) deformation decomposition, coulomb failure stress changes caused by the 2016 Menyuan earthquake, and the influence of this event on the surrounding region and active faults were analyzed. The results suggest that the 2016 Menyuan earthquake was triggered by a concomitant buried reverse fault in the northeastern part of the Northern Lenglongling Fault, which is a SW dipping sinistral thrust fault with a strike angle of 140°. The fault properties are consistent with the results of Interferometric Synthetic Aperture Radar (InSAR) 2D decompositions. The co-seismic deformation of the two satellite tracks have maximum line-of-sight uplifts of 55 mm and 65 mm, without notable subsidence. The post-seismic effect of the earthquake mainly affected the area between the Lenglongling Fault and the Northern Lenglongling Fault. The earthquake caused stress loading on the southwest of the western segment of the Lenglongling Fault and on the southeast of the eastern segment of the Northern Lenglongling Fault, as well as along these two faults.

Investigation of coseismic liquefaction‐induced ground deformation associated with the 2019 Mw 5.8 Mirpur, Pakistan, earthquake using near‐surface electrical resistivity tomography and geological data

ABSTRACTAn electrical resistivity tomography survey was conducted to assess the subsurface conditions associated with the coseismic liquefaction phenomenon in the epicentral region following the Mw 5.8 Mirpur earthquake (Pakistan) on 24 September 2019. The Mirpur earthquake produced extensive coseismic liquefaction‐induced surface deformations, including: sand blows, ground failure and lateral spreading along the Upper Jhelum Canal and in the nearby villages. Electrical resistivity data were acquired along three profiles and calibrated with available borehole data. The inverted electrical resistivity tomography profiles reveal three regional geoelectric layers, which consist of an upper 2–‐5‐m‐thick discontinuous zones of medium resistivity values ranging from 25 Ωm to 60 Ωm, underlain by a 7–8‐m‐thick zone of low resistivity (<10 Ωm) and a basal layer of high resistivity (> 100 Ωm). Based on geological and geophysical data, we infer that. (1) disrupted geoelectric layers in the shallow subsurface and spatially extended low electrical resistivity (<8 Ωm) layers document the elevated groundwater table due to sudden increase in pore‐water pressure triggered by the Mirpur earthquake. These lenses of high conductivity may represent potential hazards in the case of future earthquakes in the study area. (2) Fracture azimuths vary between 120° ± 15° and 335°–45° (subparallel and orthogonal to the strike of the Himalayan Frontal Thrust. (3) Common coseismic deformational features (e.g., sand blow and ground fracture) are located within the zone of maximum‐recorded ground shaking (intensity of VI) and underlain by Quaternary alluvial sediments. (4) Mega fractures (1.60 m wide and up to 187 m long) oriented parallel to the canal resulted from lateral spreading. We conclude that high resistivity structures extending from depth to the shallow subsurface resulted from either intrusion of air or eruption of sands from layer three. We suggest that high‐resolution geoelectrical imaging is a valuable complementary tool for evaluating the extent of subsurface liquefaction features and in understanding coseismic deformation during earthquakes, which can help with seismic hazard analysis and mitigation in seismically active regions.

An Assessment of Earthquake Scaling Relationships for Crustal Earthquakes in Indonesia

AbstractTo estimate the hazard posed by active faults, estimates of the maximum magnitude earthquake that could occur on the fault are needed. I compare previously published scaling relationships between earthquake magnitude and rupture length with data from recent earthquakes in Indonesia. I compile a total amount of 13 literatures on investigating coseismic deformation in Indonesia, which then divided into strike-slip and dip-slip earthquake cases. I demonstrate that a different scaling relationship generates different misfit compared to data. For a practical practice of making seismic hazard model in Indonesia, this research shows the suggested reference for a scaling relationship of strike-slip and dip-slip faulting regime. On a practical approach in constructing a logic tree for seismic hazard model, using different weighting between each published earthquake scaling relationship is recommended.

Bookshelf Kinematics and the Effect of Dilatation on Fault Zone Inelastic Deformation: Examples From Optical Image Correlation Measurements of the 2019 Ridgecrest Earthquake Sequence

AbstractThe 2019 Ridgecrest earthquake sequence initiated on July 4th with a series of foreshocks, including an Mw 6.4 event, that culminated a day later with the Mw 7.1 mainshock and resulted in rupture of a set of cross‐faults. In this study, we use subpixel correlation of optical satellite imagery to measure the displacement, finite strain, and rotation of the near‐field coseismic deformation to understand the kinematics of strain release along the surface ruptures. We find the average off‐fault deformation along the mainshock rupture is 34% and is significantly higher along the foreshock rupture (56%), suggesting it is a less structurally developed fault system. Measurements of the 2D dilatational strain along the mainshock rupture show a dependency of the width of inelastic strain with the degree of fault extension and contraction, indicating wider fault zones under extension than under shear. Measurements of the vorticity along the main, dextral rupture show that conjugate sinistral faults are embedded within zones of large clockwise rotations caused by the transition of strain beyond the tips of dextral faults leading to bookshelf kinematics. These rotations and bookshelf slip can explain why faults of different shear senses do not intersect one another and the occurrence of pervasive and mechanically unfavorable cross‐faulting in this region. Understanding the causes for the variation of fault zone widths along surface ruptures has importance for reducing the epistemic uncertainty of probabilistic models of distributed rupture that will, in turn, provide more precise estimates of the hazard distributed rupture poses to nearby infrastructure.

Sentinel-1 SAR-Based coseismic deformation monitoring service for rapid geodetic imaging of global earthquakes

Geodetic observation imaging technology, such as interferometric synthetic aperture radar (InSAR), has become essential for describing the dimensions and spatial complexity of earthquakes. The Sentinel-1 constellation provides an unprecedented intensive radar image acquisition ability. The amount and availability of SAR images have exponentially increased since the constellation was launched, and it has significantly contributed to the on-going big data era. In this paper, we use the capabilities of Sentinel-1 SAR to develop a fully automated coseismic deformation monitoring service and produce value-added products to support the monitoring of earthquake disasters. This monitoring service is implemented under the modern processing environment of WebGIS to generate geocoded interferograms around areas affected by earthquakes. We describe a detailed workflow for earthquake response using Sentinel-1 SAR images and provide a preliminary process for exploiting Sentinel-1 InSAR at an operational level in support of global earthquake emergency response.

Deriving Centimeter-Level Coseismic Deformation and Fault Geometries of Small-To-Moderate Earthquakes From Time-Series Sentinel-1 SAR Images

Small-to-moderate earthquakes (e.g. ≤Mw5.5) occur much more frequently than large ones (e.g. >Mw6.0), yet are difficult to study with InSAR due to their weak surface deformation that are severely contaminated by atmospheric delays. Here we propose a stacking method using time-series SAR images that can effectively suppress atmospheric phase screens and extract weak coseismic deformation in centimeter to sub-centimeter level. Using this method, we successfully derive coseismic surface deformations for three small-to-moderate (Mw∼5) earthquakes in Tibet Plateau and Tienshan region from time-series Sentinel-1 SAR images, with peak line-of-sight deformation ranging from 5–6 mm to 13 mm. We also propose a strategy to downsample interferograms with weak deformation signal based on quadtree mesh obtained from preliminary slip model. With the downsampled datasets, we invert for the centroid locations, fault geometries and slips of these events. Our results demonstrate the potential of using time-series InSAR images to enrich earthquake catalog with geodetic observations for further study of earthquake cycle and active tectonics.

Co-Seismic Inversion and Post-Seismic Deformation Mechanism Analysis of 2019 California Earthquake

In July 2019, a series of seismic events, including a magnitude (Mw) 7.1 mainshock and Mw 6.4 foreshock, occurred in Eastern California. Studying these seismic events can significantly improve our understanding of the Eastern California tectonic environment. Sentinel-1A and ALOS-2 PALSAR images were utilized to obtain co-seismic deformation fields, including mainshock and foreshock deformation. The Okada elastic dislocation model and ascending and descending orbit results were used to invert the co-seismic slip distribution and obtain a co-seismic focal mechanism solution. Using ascending Sentinel-1A images, a time-series deformation was obtained for 402 d after the earthquake, and the deformation evolution mechanism was analyzed. The maximum uplift caused by the co-seismic mechanism reached 1.5 m in the line of sight (LOS), and the maximum subsidence reached 1 m in the LOS. For 402 d after the earthquake, the area remained active, and its deformation was dominated by after-slip. The co-seismic inversion results illustrated that California earthquakes were mainly strike-slip. The co-seismic inversion magnitude was approximately Mw 7.08. The Coulomb stress change illustrated that the seismic moment caused by the co-seismic slip was 4.24 × 1026 N × m, which is approximately Mw 7.06. This finding is consistent with the co-seismic slip distribution inversion results.

Source Characteristics of the 2020 Mw 7.4 Oaxaca, Mexico, Earthquake Estimated from GPS, InSAR, and Teleseismic Waveforms

AbstractOn 23 June 2020, an Mw 7.4 earthquake struck offshore Oaxaca, Mexico, providing a unique opportunity to understand the seismogenic tectonics of the Mexican subduction zone. In this study, near-field coseismic deformation caused by the event was retrieved from Global Positioning System (GPS) observations and Interferometric Synthetic Aperture Radar (InSAR) measurements. Given static geodetic measurements, high-rate GPS waveforms, and teleseismic waveforms, the fault geometry and rupture process for the 2020 Oaxaca earthquake were robustly determined by nonlinear joint inversions. The main slip was located at a depth of 20–30 km with a peak slip of 3.4 m near the epicenter. The total released moment was 1.70×1020 N·m, corresponding to Mw 7.4. The whole rupture process lasted 14 s, with the dominant rupture slip occurring 5–8 s after initial rupture. The mainshock rupture mostly occurred along the fault strike, covering a size of ∼55 km(along strike)×∼35 km(along dip) and totally overlapping with the 1965 Mw 7.5 rupture zone. We speculate that this 2020 earthquake is a repeat event following that in 1965. Fluid percolation under the slab may be one of the key factors affecting the seismogenic depth in the Oaxaca region.

Implications of the temporal variations of geoid heights over South American vertical reference frames

The temporal variations in a vertical reference frame depend on the variations in the reference surface (e.g., the geoid), and in the surface where the benchmarks are located. The mass redistribution on and beneath the Earth’s surface generates changes in the geoid, which is the reference surface for orthometric heights. To model the phenomena and processes that affect Earth’s gravity field, the maintenance of a high-precision global physical reference frame that considers its temporal variations is necessary. In this contribution, we estimate and analyze the impact of three geophysical signals, namely mega-earthquakes (Mw > 7.5), hydrological loadings, and glacial isostatic adjustment over the South American vertical reference frames based on the Gravity Recovery and Climate Experiment monthly solutions, glacial isostatic adjustment, and hydrological models. Our results reveal that long-term trends range from −0.5 to 0.3 mm/year, which implies possible height variations up to 10 mm over 20 years. These results point out the possibilities for maintaining modern vertical reference frames if variations in the trends (e.g., due to accelerations) are disregarded. The seasonal variations (from peak to peak), co-seismic deformation, and post-seismic deformation reach 31 mm, 3.8 mm, and 0.8 mm, respectively. According to wavelet analysis based on the independent components (IC) obtained from independent component analysis, it was observed that the predominant signal has one cycle per year. The first four ICs represent 94.4% of the geoid variability. The spatial patterns of the four modes indicated that geoid variations are concentrated in the Amazon, Tocantins, Parana, and Sao Francisco river basins. Temporal variations of the geoid in South America reach magnitudes that should be considered in the evolution of height systems to accomplish the requirements of a modern height system (accuracy on the order of 10 mm or better).

Internal co-seismic displacement and strain changes inside a homogeneous spherical Earth

SUMMARYIn this study, we devised a new set of analytical foundation solutions to compute the internal co-seismic displacement and strain changes caused by four independent point sources (strike-slip, dip-slip, horizontal tensile and vertical tensile) inside a homogeneous spherical earth model. Our model provides constraints on the deformation properties at depth and reveals that the internal co-seismic deformation is larger than that on the surface. The deformation near the source is convergent with our formulae. For the internal deformation at radial section plane, the patterns of horizontal displacements ${u_\theta },{u_\phi }$ and strain changes ${e_{{ rr}}},{e_{\theta \theta }},{e_{\phi \phi }},{e_{\theta \phi }}$ caused by strike-slip and tensile sources appear symmetric at the equidistance above and below the source. Their amplitudes are not identical but with a small discrepancy actually. Unlike these, the patterns of radial displacements ${u_r}$ for strike-slip and tensile sources exhibit point symmetry with the equidistance from the source. Also, the corresponding amplitudes are slightly different. The displacements ${u_\theta },{u_\phi }$ and strain changes ${e_{{ rr}}},{e_{\theta \theta }},{e_{\phi \phi }},{e_{\theta \phi }}$ caused by dip-slip also show the same properties as ${u_{ r}}$ of the strike-slip source. The magnitudes of the displacements and strain changes depend on the source types. The curvature effect on the near-field surface deformations is small, and it increases with the studied depth. However, for the far-field deformation caused by the strike-slip source (ds = 20 km), the curvature effect can be as large as 77 per cent when the epicentral distance approximates to 1778 km.

Estimating three-dimensional coseismic deformations with the SM-VCE method based on heterogeneous SAR observations: Selection of homogeneous points and analysis of observation combinations

The previously proposed Strain Model and Variance Component Estimation (SM-VCE) method estimates three-dimensional (3-D) deformations based on heterogeneous synthetic aperture radar (SAR) observations from three or more distinct observing geometries. This method establishes an observation function by exploiting the spatial correlation of adjacent point deformations based on a geo-kinematic model (i.e., SM), and it determines an accurate weight of heterogeneous observations using the VCE algorithm; this method has been demonstrated to be superior to the traditional pixel-by-pixel-based weighted least square (WLS) method. However, since the SM-VCE method employs the adjacent points' observations to estimate 3-D deformations at a target point, it is inevitable that it results in a bias in the solution near the deformation jump area (e.g., the fault zone in an earthquake). In this paper, a Strain Model-based Adaptive Neighborhood Determining (SMAD) method is proposed to identify homogeneous deformation observations in such a way that the accuracy of the 3-D deformations estimated by the SM-VCE method can be increased, especially near the surface rupture area. This method is used for mapping 3-D coseismic deformations associated with the 2016 Mw7.8 Kaiköura earthquake in New Zealand. Furthermore, with increasing SAR data available for a single event, the effect of the number/type of independent observations on the accuracy of the 3-D deformations remains poorly understood and requires further discussion. To accomplish this goal, we define a term, the deformation dilution of precision (DDOP), to represent the quality of the 3-D deformation vector; this term is similar to the position dilution of precision (PDOP) in global navigation satellite system (GNSS), and we investigate different combinations with different numbers/types of independent observations to explore the 3-D deformations of this earthquake. The results demonstrate that the type of incorporated observations can significantly dominate the accuracy of the 3-D deformations compared to the number of observations, which can provide an important reference for relevant studies that estimate 3-D deformations. Furthermore, the proposed methods and conclusions are beneficial for estimating 3-D surface deformations associated with other geophysical processes, such as volcanic eruptions.

Tracking the recent dynamics of Mt. Vesuvius from joint investigations of ground deformation, seismicity and geofluid circulation

We reconstruct the composite dynamics of Mt. Vesuvius volcano in the period 2012–2019 from the study of ground deformation, seismicity, and geofluid (groundwater and fumarolic fluids) circulation and recognize complex spatio-temporal variations in these observables at medium (years) and short (months) time-scales. We interpret the observed patterns as the combined effect of structural changes affecting the volcanic edifice and variations of the dynamics of the hydrothermal system. In particular, we identify a change in the activity state of Mt. Vesuvius. After the activity reached minimum levels in 2014, the centroid of the surface manifestations migrated towards the SE. Episodic variations of co-seismic and aseismic deformation and fluid release, if analysed separately, would likely have been interpreted as pseudo-random oscillations of the background geophysical and geochemical signals. When organised in a comprehensive, multiparametric fashion, they shed light on the evolution of the volcano in 4D (x,y,z, time) space. These inferences play a crucial role in the formulation of civil protection scenarios for Mt. Vesuvius, a high risk, densely urbanized volcanic area which has never experienced unrest episodes in the modern era of instrumental volcanology.

Co-seismic deformation and slip distribution of 5 April 2017 Mashhad, Iran earthquake using InSAR sentinel-1A image: implication to source characterization and future seismogenesis

We analyzed interferometric synthetic aperture radar sentinel-1A-based observations to characterize the source of 5 April 2017 Mashhad, Iran mainshock (Mw 6.1), for the first time to understand the seismogenic potential of the source area using the estimates of co-seismic displacement and slip distribution on applying the steepest descent method (SDM). SAR pixel offsets (SPO) provided a deep insight into the co-seismic surface deformation of the entire source zone. Based on iterations of a total of 451 models, our analysis of sentinel-1A data from ascending and descending tracks revealed surface deformation occurred in an area of 40 × 30 km with a maximum co-seismic uplift of 10 cm. We estimated geodetic moment of 1.9 × 1020 Nm corresponding to the magnitude (Mw 6.0) of the Mashhad mainshock for which the rupture has a planner geometry with uniform slip dislocation in an elastic half-space with slip of 0.35 ± 0.1 m; strike of N313°E having dip of 48° of the thrust fault associated with oblique motion. The rupture length of 45 ± 3 km along-strike and 30 ± 3 km down dip has been estimated. The best-fit fault model geometry derived from SDM suggests that rupture occurred in the vicinity of the Kashafrud thrust fault, located west to the main Kopeh-Dagh Fault with its strike of 315°E. It is observed that a maximum slip of 0.35 m occurred at a depth of 8 km that extended to 10 km in the crust, which is found to be in unison to the Coulomb stress model that showed low-stressed zone is associated with the majority of events of lower magnitude (M ≤ 4.5) in NE–SW to the mainshock, whilst the EW zone to the mainshock found relatively highly stressed as a probable source for generating relatively higher magnitude earthquakes (M > 4.5) in the future. We infer that the estimates of co-seismic source attributes are essentially important for understanding the nature and extent of earthquake risks for Mashhad, Iran earthquake source area and of the areas of analogous geotectonic settings, elsewhere in the world.

Estimation of Coseismic Deformation With Multitemporal Radar Interferometry

Differential interferometric synthetic aperture radar (DInSAR) has been widely used as one of the most important technologies for determining coseismic deformation. However, DInSAR processing is often perturbed by errors including atmospheric effects and those in topographic models, SAR satellite orbits, and phase unwrapping operation. These nuisance components can degrade the accuracy of the measurements and, therefore, distort the inversion of fault slips especially for moderate earthquakes. We propose in this letter a multitemporal InSAR (MTInSAR) method aiming to accurately determine coseismic deformation. By jointly analyzing a set of preseismic SAR images and one postseismic image, the method allows effective separation of coseismic deformation from topographic and satellite orbital errors deformation based on the distinct spatio-temporal characteristics of the signals. Since the solution is achieved directly from wrapped differential phases, the retrieved deformation is also immune to phase unwrapping errors. The October 6, 2008 Mw 6.3 Dangxiong, China earthquake is studied with the proposed method as an example. The slip inverted, respectively, from the MTInSAR and DInSAR coseismic deformation measurements shows up to 34-cm differences, indicating that the topographic error and inaccurate removal of orbital errors can bias the fault slip inversion.

Update two-dimensional SAR offset tracking deformation time series with complex sequential least squares estimation

ABSTRACT Unlike synthetic aperture radar (SAR) interferometry, SAR offset tracking method can measure two-dimensional (2-D) large-gradient deformation with precision as 1/10 to 1/30 pixels size. In terms of 2-D deformation time series estimation, the pixel-offset small baseline subset (PO-SBAS) method was proposed. However, little research has been conducted on the dynamic estimation of 2-D deformation time series for new SAR acquisitions, which has increasing demand with the availability of SAR data. In this letter, we introduced a novel method to update 2-D deformation time series dynamically under the frame of PO-SBAS. Firstly, complex least squares (CLS) method is derived to solve the complex linear function model, and the difference between the CLS estimation in complex value and the LS estimation in real value for the real and imaginary parts, respectively, are compared. Secondly, complex sequential least squares (CSLS) estimation is proposed to update 2-D deformation time series dynamically and efficiently. Finally, both simulated and real SAR data verified the performance of the proposed method. It can be taken as a promising SAR tool for dynamic 2-D deformation estimation for the scenarios of glacier movement, mining-induced displacement, and co-seismic deformation, etc.

Effects of discontinuities inside Earth models on coseismic deformations

In this paper, we study how coseismic deformations calculated in 1066 Earth models are affected by how the models treat Earth discontinuities. From the results of applying models 1066A (continuous) and 1066B (discontinuous), we find that the difference in Love numbers of strike-slip and horizontal tensile sources are bigger than dip-slip and vertical tensile sources. Taken collectively, discontinuities have major effects on Green’s functions of four independent sources. For the near-field coseismic deformations of the 2013 Okhotsk earthquake (<i>M</i>_w 8.3), the overall differences between theoretical calculations in vertical displacement, geoid, and gravity changes caused by discontinuities are 10.52 percent, 9.07 percent and 6.19 percent, with RMS errors of 0.624 mm, 0.029 mm, and 0.063 μGal, respectively. The difference in far-field displacements is small, compared with GPS data, and we can neglect this effect. For the shallow earthquake, 2011 Tohoku-Oki earthquake (<i>M</i>_w 9.0), the differences in near-field displacements are 0.030 m (N-S), 0.093 m (E-W), and 0.025 m (up-down) in our study area with the ARIA slip model, which gives results closer to GPS data than those from the USGS model. The difference in vertical displacements and gravity changes on the Earth’s surface caused by discontinuities are larger than 10 percent. The difference in the theoretical gravity changes at spatially fixed points truncated to degrees 60, as required by GRACE data, is 0.0016 μGal and the discrepancy is 11 percent, with the theoretical spatial gravity changes from 1066B closer to observations than from 1066A. The results show that an Earth model with discontinuities in the medium has a large effect on the calculated coseismic deformations.

4-② 地震前後の衛星SAR画像解析とレーザ地形データ差分解析による造成地周辺の地盤変位

4-② 地震前後の衛星SAR画像解析とレーザ地形データ差分解析による造成地周辺の地盤変位

Co-Seismic Deformation of the 2017 Mw 6.6 Bodrum–Kos Earthquake in Speleothems of Korakia Cave (Pserimos, Dodecanese, Greece)

Co-Seismic Deformation of the 2017 Mw 6.6 Bodrum–Kos Earthquake in Speleothems of Korakia Cave (Pserimos, Dodecanese, Greece)