Synthetic Aperture Radar Interferometry (InSAR) is utilized to evaluate slope stability, revealing pronounced periodic oscillations in the deformation time series. Although such periodic patterns have conventionally been ascribed to stratified tropospheric delays or seasonal precipitation in prior studies, periodic signals persist in the deformation results even after atmospheric phase removal by a linear iterative model. This observation underscores the limitations of conventional deformation interpretations and prompts further investigation into the underlying physical mechanisms. To address this, an interferometric phase correction model accounting for variations in surface dielectric property has been proposed. This model effectively removes phase delays induced by dielectric property changes from the raw interferometric phase, enabling the extraction of linear trend signals that reflect actual surface deformation. To verify the reliability of the correction model, Sentinel-1A (C-band) and TerraSAR-X (X-band) radar data is employed to quantify deformation patterns in the slope of non-sliding section around the Huangnibazi landslide. The analysis consistently identifies periodic deformation signals in both SAR datasets after mitigating atmospheric influences. Our findings indicate that dielectric property changes constitute a critical factor in InSAR deformation monitoring that cannot be overlooked. The observed periodic fluctuations in deformation time series are attributed to dielectric-induced phase modulation effects. Furthermore, systematic correlation analyses confirm a strong coherence between soil moisture variations and deformation fluctuations, with minimal temporal hysteresis. In contrast, seasonal precipitation exhibits a weaker correlation with deformation and longer hysteresis time. These results robustly support the theoretical framework linking soil moisture, dielectric property, penetration depth, and phase delay. This insight holds significant implications for enhancing the effectiveness of InSAR technology in slope disaster monitoring and early warning systems.

Microwave Brightness Temperature (${T} _{\text {B}}$) anomalies preceding strong earthquakes have been frequently observed by satellite microwave remote sensing. To reveal the physical mechanism of the pre-earthquake${T} _{\text {B}}$anomalies, rock mechanics experiments have been conducted through microwave radiation observation at low stress levels, and only weak microwave radiation has been detected, which is insufficient to detect by satellite microwave sensors. This is inconsistent with the strong pre-earthquake${T} _{\text {B}}$anomalies monitored by satellite microwave remote sensing. In this study, a microwave observation experiment of rock under tiered cyclic loading with a gradually increasing cyclic stress was conducted to investigate the${T} _{\text {B}}$variation throughout the elastic deformation and failure process. The experimental results illustrate that the${T} _{\text {B}}$and stress continuously maintain a positive correlation, with a linear correlation coefficient greater than 0.90. A stronger${T} _{\text {B}}$variation of 3.07 K than the previous experimental results is observed at a high stress change of 96 MPa, which is quantitatively in the same order as the${T} _{\text {B}}$anomalies detected by satellite microwave remote sensing. With the stress increases, the${T} _{\text {B}}$variation decreases shortly preceding rock failure due to the formation of fractures, which is in agreement with the short-term weakening of pre-earthquake${T} _{\text {B}}$anomalies. The outcome of this study promotes the understanding of pre-earthquake${T} _{\text {B}}$anomalies detected by satellite microwave remote sensing.

Many studies have confirmed that the microwave radiation of rock materials will change with compressive stress and pore water. However, how the presence of pore water in rock volume influences the stress-induced change in microwave radiation ($\Delta T_{B}$) is not clear. In this study, both the air-dry and humid (partially saturated) sandstone specimens were loaded compressively and the C-band (6.9 GHz) microwave radiometer was used to investigate the change of$T_{B}$and the differences of$\Delta T_{B}$. The experimental results illustrated that the presence of pore water in sandstone promotes significantly the relationship between the positive$\Delta T_{B}$and the applied compressive load. On the basis of radiative transfer theory and effective dielectric constant model of multiple-phase media, we found that$\Delta T_{B}$of sandstone mainly results from the compressive stress distributed on mineral grains, which is able to reduce the dielectric constant of minerals and lead to the increase of microwave radiation. For dry sandstone, the distribution of compressive stress on minerals is mainly controlled by grain contact, while for humid sandstone, the pore water plays an important role in applying uniform pressure on grain surface and reducing the dielectric constant of grains; thus, the effective dielectric constant of rock volume is sensitive to the applied loads on partially saturated specimen. This study is important for understanding the positive$T_{B}$anomalies prior to large tectonic earthquakes in condition of ground surface rock partially saturated and is valuable to uncover potential$T_{B}$anomaly related to seismic activities.

Incidence angles ( θ) and polarization modes ( p) are the essential factors for detecting earthquake (EQ)-related microwave radiation anomalies. However, their influences are still not well studied. In this article, research was carried out to simulate the observation of satellite on EQ under different θ and p. The microwave observation experiments were performed on granite samples pressed with θ from 0° to 30°, as well as vertical (v) to horizontal (h) polarizations under weak radiation environment. It was found that the stress-induced changes ( ΔTB) in the samples' microwave brightness temperature ( TB) are anisotropic and polarized. It was observed that the trends of ΔTBmay be reversed under different θ ( p), with a probability of 57.14% (14.29%). The magnitude of ΔTBat h is also prone to greater changes than that at v, with a probability of 67.86%. Theoretical analysis was performed based on crystal optics, Fresnel formulas, and dielectric physics. This phenomenon may relate to the combined action of piezoelectric effect, extension and contraction of ionic bonds, and turning-direction polarization. The sensitivity of TBto the change in permittivity was analyzed by theoretical simulation in order to reveal the effects of modification in θ and p on the TBchange in stress of rock. For rocks with permittivity ε = 7 - i0.3, the most and least sensitive θ are near 52° at h polarization and 69° at v polarization, respectively. Finally, the significance of these results was discussed.

Generally, ground stress accumulates in the process of earthquake (EQ) preparation. The change trend of microwave brightness temperature (TB) of rock with stress change is an important factor for the understanding of the microwave anomalies associated with EQs. However, it is not yet clear whether the downtrend of rocks' TB is associated with increased stress. To confirm this, in this article, the instantaneous field of view of the microwave radiometer was identified first. Then, the microwave observation experiments were conducted on granite samples at 6.6 GHz under cyclic loading and outdoor conditions with weak background radiation. It was found that besides uptrend and fluctuation, the downtrend of granite samples' TB also correlates with stress, with an occurrence probability of 47.62% and a maximum rate of -0.038 K/MPa. The variation trends of TB with stress are not uniform across different areas of the same sample. To reveal the cause of this phenomenon, the permittivity of single-crystal quartz, one of the main mineral compositions of granite, was measured when it was under compassion loading at the direction perpendicular or parallel to the optical axis. For quartz, the real part of the permittivity rises (falls) when the two directions are perpendicular (parallel), causing the TB to fall (rise). The optic axes of minerals are randomly distributed in granite samples, which make the variation in the permittivity of minerals also random, thereby resulting in the nonuniformity of stress-induced TB variation in granite samples. Finally, the implications of these results were discussed.

The additional microwave radiation from underground rock mass (lithosphere) that is caused by tectonic activity and alternating crustal stress has been shown to be a detectable electromagnetic signal via satellite remote sensing. However, the emission of microwave radiation produced inside the lithosphere will be affected by its overburden matter, such as sand, soil, water, and vegetation, and this effect is unknown. In this article, we use a C-band microwave radiometer to detect the variations in the microwave brightness temperature (TB) of rock samples in the process of axial loading. For the rock samples, the surface was bare and covered with dry sand or humid sand. The experimental detection illustrates that the dry sand unexpectedly allows more stress-associated additional radiation (ATB) to be received by the radiometer, while humid sand shows significant extinction of ATB. Both the radiative transfer theory and the stress-activated positive hole hypothesis are applied to interpret the mechanisms of the effect of dry and humid sand layers on ATB. The outflow of stress-activated positive holes is from inside the loaded rock, and hence their accumulation beneath the surface of the sand layer is expected to reduce the local dielectric permittivity of sand, thereby making the detected ATB by the microwave radiometer to be larger than that extrapolated theoretically in accordance with radiative transfer theory. This article is valuable for understanding the diverse TB anomalies that have been observed prior to tectonic earthquakes, and it facilitates the evaluation of the potential application of ATB to seismic monitoring and earthquake prediction.

Land subsidence, as a regional environmental disaster problem, hinders social stability and sustainable development, and endangers people's lives and property in the long term. As demonstrated by many examples, Time Series InSAR is able to monitor land subsidence using a stack of synthetic aperture radar(SAR) images.However, due to the data missing problem caused by short satellite life and data confidentiality, it is difficult to get the full monitoring result during long time by using only a single sensor. In recent years,multi-sensor InSAR fusion methods are mostly used for cross validation and comparative analysis. Unfortunately,the datasets used in these methods is repetitive and cohesive in short time, the problem of missing data during long time has not been solved.In this paper, we will exploit three stacks of time-gapped SAR data, acquired from 2004 to 2005 by Envisat ASAR, from 2007 to 2010 by ALOS PALSAR, from 2015 to 2016 by TerraSAR-X/TanDEM-X, to analyze the long term subsidence of Shenyang city. In order to fuse the time-series InSAR results from different sensors, mathematical methods based on nonlinear curve fit will be conducted to find the best-fit model for the deformation time series.We also examine the performance of the nonlinear curve fit by calculating the root mean square error (RMSE) based on the difference between the vertical deformation time series and the best-fit model.

At present, the earth surface stress monitoring mainly relies on the ground drilling method. Affected by test conditions and cost, the large-scale and regional stress measurement cannot be realized by traditional methods in the actual measurement. As the ground information at the large scale can be observation by satellite in all-weather condition, it is possible for detecting the stress information via the satellite remote sensing. In this paper, the experimental studies on the microwave and thermal infrared spectrum of loaded rock were carried out. Based on the experimental results, the possibility for detecting the earth surface stress condition via remote sensing was discussed. This study demonstrates the potential ability to use satellite remote sensing to observe ground stress condition and earthquakes.

To simulate the actual satellite observation situation of crust rock on the land surface, the thermal infrared spectrum observation experiment of loaded quartz sandstone was carried out in the cold sky background. In order to analysis the mechanism of radiation variation due to stress, the spectrum observation comparison experiment of the sample in the heating process is conducted as well. The experimental results indicate that the spectral radiance variation features in the loading process is different from that in the heating process. The trend of the two variation curves are opposite in the range of 8.0-9.7μm, which is corresponding to the wave range of reststrahlen features (RF) of the spectral emissivity. The factors affecting the radiance variation are analyzed. It can be concluded that the radiance increase in the compressed loading process is caused by both the temperature and the emissivity change. The results indicate that it is probable to establish a relationship between the emissivity and stress and provide an experimental basis for the observation of the stress by means of the infrared remote sensing.

In mining areas, wastes are usually piled-up in the dump, making a man-made hill with height of more than tens of meters. Because of the loose structure of dump sites, landslides or debris flow may occur after heavy rainfall, threatening local people's lives and properties. Therefore, dump stability monitoring and early warning for possible hazards is crucial for ensuring local safety. In this paper, a collaborative stability analysis with high-resolution SAR data and ground measurements is conducted over Xudonggou dump of Anqian iron mine. A two-pass DInSAR analysis is carried out to derive the deformation distribution over the whole area. High-precision GPS and robotic measurements on several points are also conducted over the dump site. Based on the measurements, an slope stability analysis is carried out and eventually a landslide hazard zone is outlined.

Previous studies have shown that thermal infrared anomalies can be detected in the crust rocks in satellite infrared images before an earthquake. However, thermal infrared remote sensing is easily affected by weather conditions because of the short wavelength of infrared radiation. In this paper, instead of infrared radiation, we focus on the microwave radiation characteristics of loaded rock. First, a microwave observation system was built to observe the loading process of rocks in an outdoor environment with a cold sky background. Then, the microwave radiation changes in the loaded granite samples during elastic deformation and fracturing stages were analyzed. The experiments yielded the following results. First, the microwave brightness temperature has a linear positive correlation with the load in the elastic deformation stage of the granite samples, and lateral pressure accelerates the changes in the microwave radiation. Second, the microwave brightness temperature usually decreases as the rock develops layered fractures but increases as the rock develops surface fractures, which significantly alter the surface morphology and roughness. The mechanisms responsible for the changes in microwave radiation during the rock deformation and fracturing processes are discussed. This study demonstrates the potential ability to use microwave-sensing satellites to observe seismogenic processes and earthquakes.

Solar activity dependency of the ionosphere in local region during a short timescale is of great importance for the analysis of ionospheric anomalies probably caused by local events such as earthquakes and volcanic eruptions. Recently, a nonlinear background removal method based on multiresolution wavelet transform (MWT) for seismo-ionospheric anomaly analysis has been developed by He et al. To further evaluate the method performance, three years of different solar activity levels have been chosen to examine the relationship between the TEC variations and solar activities during 23rd solar cycle. The results showed that the MWT-based method is able to handle well the solar radiation background in the ionospheric TEC data, especially under a complex solar activity situation.

A violent earthquake (Ms 7.1) occurred in Yushu county of China on April 14, 2010, and the epicenter was (33.1°N, 96.7°E). It caused 2689 people death. We use the AMER-E satellite remote sensing data to analyze the variation of microwave radiation around the epicenter. It was found 45 days before the earthquake a high microwave radiation strip appeared in the southwest of the epicenter, and gradually became longer and wider. The largest increment of microwave brightness temperature was up to 12K. 9 days before earthquake another high microwave radiation strip appeared in the northwest of the epicenter and the epicenter was just in the intersection of the two the high microwave radiation strips. 4 days before the earthquake the strength of the microwave anomaly became weak, but one day before the earthquake the strength became increase again. After the main shock the anomaly still existed for about 20days and was finally disappeared. To explore the cause of microwave radiation anomaly the microwave polarization difference index (MPDI) and the air temperature variation was investigated. The final result indicated the microwave anomaly was caused by the temperature increase, i.e. the anomaly should belong to thermal anomaly.

The anomaly of SLHF, which is a key component of the Earth's energy balance and represents the heat flux from the Earth's surface to the atmosphere associated with evaporation or transpiration of water on the surface and subsequent condensation of water vapor in the troposphere, has been widely reported as a possible earthquake precursor. The causes are generally attributed to the increase in infrared thermal (IR) temperature and the air ionization produced by increased emanation of radon from the Earth's crust. In this paper, the theoretical analysis and case study show that there is close relationship between soil moisture and SLHF anomalies. For inland earthquakes, the increase of soil moisture due to the rising of groundwater level will bring with higher potential evaporation, leading to the increase of latent heat flux. Further study with more accurate soil moisture product after the new satellite mission will help us to better understand the influence of soil moisture on SLHF variation and their relations with seismogenic process.

The GEOSS under construction is providing space-,aero-,ground/sea-based multiple observations on planet Earth for the seismogenic process monitoring and earthquake precaution. The stress enhancement and energy accumulation in seismic activity area change locally the physical parameters of lithosphere with the developing of a series of effects that can comprise most of the following ones: initial cracks, the fracturing of rockmass, the changing of electromagnetic properties, the decreasing of dielectric constant, the re-activation of P-holes, the leaking of pore-gas, and the rise of water-level. The physical states of coversphere and atmosphere are to be affected due to the lithosphere-coversphere-atmosphere (LCA) coupling, and the signals from the underground, surface, and atmosphere to satellites are to be changed with parameter anomaly. We suggested that the LCA coupling is important for understanding GEOSS observations, especially for earthquake anomaly recognition (EAR). Using deviation-time-space-thermal (DTS-T) method for EAR, three recent major earthquakes (2009 Italy L'Aquila earthquake, 2010 China Yushu earthquake and 2010-2011 New Zealand earthquake sequence) are taken as typical cases for analysis to the multi-parameters anomalies, preceding the shocking, with quasi-synchronism and geo-consistency. The specific LCA coupling effects related with the earthquakes are also discussed in brief.

Although earthquakes are difficult to be predicted because of the complexity of the Earth system and the uncertainty of seismogenic processes, GEOSS provides multiple sources of observation data and brings a possibility to extract a thermal anomaly that would have a significant effect on earthquake prediction. Referring to the analysis on the lithosphere-coversphere-atmosphere (LCA) coupling due to stress enhancement in seismogenic zone, six thermal parameters, including surface latent heat flux (SLHF), thermal infrared radiation (TIR), outgoing longwave radiation (OLR), diurnal temperature range (DTR), atmospheric temperature, and skin temperature, are selected for GEOSS-based earthquake anomaly recognition (EAR). The inherent relations between the six thermal parameters are preliminarily introduced in consideration of possible LCA coupling. With overquantity, quasi-synchronism, and geo-consistency being defined as three rules for data mining, a deviation-time-space-thermal (DTS-T) EAR method as well as its procedures are developed in this paper. With 2008 M7.3 Yutian earthquake, China, 2008 M8.0 Wenchuan earthquake, China, and 2010 M7.1 Christchurch earthquake, New Zealand, being examples of tectonic earthquakes, the technical procedures of DTS-T method are demonstrated, which show that the obtained compositive thermal anomaly has a significant effect on earthquake prediction.

In this paper, we proposed a wavelet-based methodology that enables to detect and diagnose the ionospheric anomalies associated with seismic activity. Wavelet transform and cross-wavelet analysis methods are used to detect and identify the spatio-temporal variability of ionospheric perturbation associated with Wenchuan Ms8.0 earthquake, 12 May 2008 in China, and to gain further insights into the dynamical relations between the ionospheric anomaly variability and the geophysical indices variability in the same span of observations, 12 April ~ 12 May, 2008. The details of the algorithm and the analysis results are introduced in this paper.

Some authors reported that there were anomalies appearing in the satellite remote sensing information before earthquake, including thermal infrared anomaly, water vapor anomaly and microwave anomaly etc. But how to obtain the actual anomaly from the complicated remote sensing information is very difficult due to the influencing of many factors, such as terrain, physiognomy, geological condition, and weather etc. Meanwhile the explaining of anomaly mechanism is another difficultly. In this paper, a new method is proposed to extract the microwave radiation anomaly before Wenchuan earthquake from the AMER-E satellite remote sensing data. The method can eliminate the influencing of terrain, physiognomy and weather. The result of anomaly analysis shows that there was microwave anomaly before and after the main shock of Wenchuan earthquake. In order to explore the anomaly mechanism a physical simulation experiment was carried out. The experimental result shows that the microwave brightness temperature increases in the elastic stage, decreases in the plastic stage, and increases again in the fracturing stage. Based on the experimental result the anomaly mechanism is discussed.

The satellite remote sensing has become a promising technique for detecting earthquake and fault activities. But the radiation and the reflection of the earth surface detected by remote sensing are influenced not only by earthquake or fault activities but also by many factors such as terrain, vegetation, weather and so on. In order to effectively extract the earthquake anomaly and get rid of the impacts of non-earthquake factors, this paper presented a new method to extract and analyze anomaly caused by earthquakes or fault activities. We applied the method to the data of AMSR-E and MODIS for the earthquake that struck Sichuan, China, on May 12, 2008. As a result, we detected that the thermal infrared (TIR) anomaly information retrieved from MODIS data emerged before the earthquake and the microwave radiation anomaly retrieved from AMSR-E data emerged both before and after the earthquake.

Although thermal infrared (TIR) imaging technology has been successfully applied in the thermographic inspection of engineering defects and landmines, its use for detecting water permeation on field large-scale rock relics is new. Huashan Rock Painting, a world-famous field large-scale rock relic in Guangxi Province, China, was used as a case for TIR imaging detection of water permeation on field large-scale rock relics. This paper introduced detection methods, a key parameter, and a gradation model for TIR imaging. Three detection methods were specially designed and used in two experiments performed during the drought and rainy seasons, respectively. Thermographic features were comprehensively analyzed, and temperature variation curves of water-permeation places were quantitatively compared with those of places unaffected by water permeation. Water-permeation places can be precisely identified based on thermographic features and temperature variation curves. Physical interpretation was conducted based on the heat transfer equation and on the Stefan-Boltzmann law. The minimum temperature of solar irradiated water-permeation places was selected as the key parameter, and a -based model was established for water-permeation gradation. To strengthen the differences between water-permeation places and places unaffected by water permeation, TIR imaging should also be conducted during a sunny day after the rains, particularly during an intermittent sunny day after heavy rains in the rainy season. It is the best time for TIR-imaging-based water-permeation detection and gradation.

Remote sensing data have been used to analyze the changes in column water vapor in response to the Wenchuan Ms 8.0 earthquake, occurred in China on May 12, 2008. Anomalous changes in water vapor content have been found over the epicentral and surrounding regions 11 days before the earthquake. The sudden increase in water vapor content in the atmosphere before the earthquake may be attributed to the increase in evaporation due to increase in land surface temperature. The brightness temperature of land surface around the epicenter is found to increase one day before the increase in the water vapor content.

The environment and vegetation cover in mining area are influenced by the exploitation and utilization of mineral resources. It needs dynamic monitoring and estimation by the help of satellite remote sensing technology. Taking SPOT-VGT NDVI as information source and considering the characteristics of mining areas in China, this paper researched how to monitor the vegetation variation and desertification in mining area. The method includes the composition of time series data, the vegetation variation analysis and the gradation of desertification land. Concretely, the variation of NDVI is divided into 7 levels according to the slope of the fitted line by using NDVI time series data. Besides, the desertification land is divided into 5 levels according to the vegetation coverage, which is transformed from NDVI. The presented method was validated in Ningdong coal mining area, northwest China, and the results showed that the method is valid and effective.

The satellite TIR remote sensing has become a promising technique for monitoring tectonic activities and detecting earthquake precursors due to the advantages of large observation area and short observation period. In order to identify and to extract the TIR anomaly, several presented methods are tested and compared in this paper. The comparison results indicate that Robust AVHRR Technology (RAT) is a better method for detecting pre-earthquake thermal anomaly. Anyway RAT is not able to quantitatively analyze the TIR anomaly before shock. RAT method is hence improved for obtaining the value of area and average temperature of TIR anomaly. Based on the analysis of some tectonic earthquakes, an empirical quantitative model for tectonic activity analysis and earthquake magnitude predication is established.

The phenomenon of a satellite thermal infrared (TIR) anomaly before earthquakes has been reported since the late 1980s. The reported increase of surface temperatures reaches 2-4 degC, occasionally higher. Usually, the anomaly appears one month to several days before the earthquake. Several mechanisms of hypothesis have been put forward to interpret the reported temperature increase. In this paper, the satellite TIR anomaly features of four earthquakes in the Taiwan region are first analyzed. To study the mechanisms of infrared anomaly a group of physical simulation experiments are carried out. The mechanism of the satellite Infrared anomaly before an earthquake in the Taiwan region is discussed based on the experimental results. Furthermore, a preliminary model for tectonic activity analysis and for short-term earthquake prediction based on the analysis of the satellite infrared anomaly before an earthquake in the Taiwan region is presented.

This paper briefly introduces the general scientific facts from the reports on satellite thermal infrared (TIR) anomaly before earthquake and the presented mechanism and hypothesis for interpretation the TIR anomaly. The spatio-temporal features of infrared (IR) radiation from loaded rock, stick-sliding rock and simulated active fault motion based on experimental IR detection are also introduced. Especially, the experiments on simulated fault activity shows that the TIR anomaly is likely to develop along the primary fault and the both sides of wedge-shaped acute geo-block in condition of intersected fault system, and that the intersection location is usually the coming epicenter. The theoretical mechanism of TIR anomaly before tectonic earthquake is hence suggested to be stress-thermal effect accompanied and strengthened by hydro-geological effect, greenhouse effect, P-hole effect and so on. As a case, the spatio-temporal features of TIR before Zhangbei Ms6.2 1998 earthquake is theoretically analyzed based on the overlay of active fault system on NOAA-AVHHR satellite TIR images. It was discovered that TIR anomaly is controlled by a potential great deep active fault and that the epicenter is exactly the intersection point of the primary great fault and two secondary faults being tow sides of an acute wedge-shaped active geo-block. It is concluded that although the earthquake is a complex and uncertain process of crust motion, the predication of earthquake is not impossible. Referring to the developing GEOSS and generalized remote sensing (GRS), a preliminary procedure for comprehensive multiple parameters analysis on fault activities and earthquake early warning is presented, which is based on massive data fusion.

Dongsha Ms5.9 earthquake and Zhangbei Ms6.2 earthquake are used to analyze the spatial-temporal features of satellite positive TIR anomaly before shock. Four experiments with rock blocks to simulate the tectonic earthquakes and TIR anomaly are introduced. It revealed that (1) the positive TIR anomaly usually develops along active faults, especially along chief faults; (2) the spatio-temporal features of TIR anomaly and precursors are tightly related to regional geological structure and local active faults; (3) the intersection position of faults is always the sensitive seismic region with obvious positive TIR anomaly; (4) the satellite TIR monitoring on tectonic earthquake should focus on the seismic area along active faults.