Showing papers by "Geophysical Survey published in 2017"

Plate coupling and strain in the far western Aleutian arc modeled from GPS data

Abstract: The Aleutian and Kuril-Kamchatka arcs meet at a triple junction of the Pacific (PAC), Bering (BER), and North American (NAM) plates. We invert GPS observations from the westernmost Aleutian (Komandorsky) Islands and Kamchatka for the fault locking depth and block motion in the far western Aleutian transform boundary. Three boundary models were considered: (1) only the Aleutian thrust fault without a trench-normal component, (2) only a strike-slip fault in the back arc north of the Komandorsky Islands, and (3) a rigid Komandorsky sliver bounded by the Aleutian and back-arc faults. Observed velocities prefer Model 3, with a secular westward sliver velocity of 51 mm/a relative to NAM (two thirds of the total PAC-NAM motion). The observed velocities are ~10% slower because of elastic strain from boundary faults. The best fitting locking depth of faults bounding the sliver is 12 km, which is similar to depths observed in diverse tectonic environments.

Mining land subsidence monitoring using sentinel-1 sar data

Abstract: . In this paper, DInSAR technique was used to monitor land subsidence in mining area. The study area was selected in the coal mine area located in Yuanbaoshan District, Chifeng City, and Sentinel-1 data were used to carry out DInSAR techniqu. We analyzed the interferometric results by Sentinel-1 data from December 2015 to May 2016. Through the comparison of the results of DInSAR technique and the location of the mine on the optical images, it is shown that DInSAR technique can be used to effectively monitor the land subsidence caused by underground mining, and it is an effective tool for law enforcement of over-mining.

The Tolud Burst of Seismicity and the Earthquake of November 30, 2012 (MC = 5.4, MW = 4.8) that Accompanied the Start of the 2012‒2013 Tolbachik Eruption

Abstract: This paper reports a study of the Tolud earthquake sequence; the sequence was a burst of shallow seismicity between November 28 and December 7, 2012; it accompanied the initial phase in the Tolbachik Fissure Eruption of 2012‒2013. The largest earthquake (the Tolud earthquake of November 30, 2012, to be referred to as the Tolud Earthquake in what follows, with KS = 11.3, ML = 4.9, MC = 5.4, and MW = 4.8) is one of the five larger seismic events that have been recorded at depths shallower than 10 km beneath the entire Klyuchevskoi Volcanic Cluster in 1961‒2015. It was found that the Tolud earthquake sequence was the foreshock–aftershock process of the Tolud Earthquake. This is one of the larger seismicity episodes ever to have occurred in the volcanic areas of Kamchatka. Data of the Kamchatka seismic stations were used to compute some parameters for the Tolud Earthquake and its largest (ML = 4.3) aftershock; the parameters include the source parameters and mechanisms, and the moment magnitudes, since no information on these is available at the world seismological data centers. The focal mechanisms for the Tolud Earthquake and for its aftershock are consistent with seismic ruptures at a tension fault in the rift zone. Instrumental data were used to estimate the intensity of shaking due to the Tolud Earthquake. We discuss the sequence of events that was a signature of the time-dependent seismic and volcanic activity that took place in the Tolbachik zone in late November 2012 and terminated in the Tolud burst of seismicity. Based on the current ideas of the tectonics and magma sources for the Tolbachik volcanic zone, we discuss possible causes of these earthquakes.

The design of the pilotless airborne aeromagnetic instrument with compensation algorithm

Abstract: The pilotless airborne aeromagnetic instrument designed in this paper is able to locate sampling data quickly with high-efficiency and high-precision. The pilotless airborne aeromagnetic instrument can work at a large scale, and can reflect the geological effects of the ground with high resolution, and also can eliminate the effects from distractions on the ground surface and rugged area at the same time. Three-component of geomagnetic field in the pilotless aircraft magnetic heading measure system is measured by various sensors in the pilotless aircraft. The attitude angle of the aircraft is measured by the attitude control system, and can be compensated on the real-time.

Estimation of shie glacier surface movement using offset tracking technique with cosmo-skymed images

Abstract: . Movement is one of the most important characteristics of glaciers which can cause serious natural disasters. For this reason, monitoring this massive blocks is a crucial task. Synthetic Aperture Radar (SAR) can operate all day in any weather conditions and the images acquired by SAR contain intensity and phase information, which are irreplaceable advantages in monitoring the surface movement of glaciers. Moreover, a variety of techniques like DInSAR and offset tracking, based on the information of SAR images, could be applied to measure the movement. Sangwang lake, a glacial lake in the Himalayas, has great potentially danger of outburst. Shie glacier is situated at the upstream of the Sangwang lake. Hence, it is significant to monitor Shie glacier surface movement to assess the risk of outburst. In this paper, 6 high resolution COSMO-SkyMed images spanning from August to December, 2016 are applied with offset tracking technique to estimate the surface movement of Shie glacier. The maximum velocity of Shie glacier surface movement is 51 cm/d, which was observed at the end of glacier tongue, and the velocity is correlated with the change of elevation. Moreover, the glacier surface movement in summer is faster than in winter and the velocity decreases as the local temperature decreases. Based on the above conclusions, the glacier may break off at the end of tongue in the near future. The movement results extracted in this paper also illustrate the advantages of high resolution SAR images in monitoring the surface movement of small glaciers.

Development and preliminary results of a drilling core spectral imaging and cataloging system

Abstract: Drill cores provide direct evidence for geological prospecting, and compiling drill core record information has been a vital tool in geological exploration. We design and fabricate a drill core spectral imaging system that covers a wavelength range of 400 to 2500 nm with a spectral resolution of 3 to 12 nm. A visible and near infrared and a shortwave infrared spectrometer are mounted together to cover the wavelength range. This paper describes the mechanical structure, light path structure, parameters, and software processing chain of the system. With the spectral imaging system and custom-design software, a mineral core sample is analyzed to validate system performance.

CO2 Monitoring by Using VSP-FWI-Synthetic Study on CO2-saturation and pressure-buildup differentiation

Abstract: Synthetic study on CO2-saturation and pressure-buildup differentiation by using VSP-FWI is conducted in a virtual CCS site. Geophysical and Reservoir simulation works are first implemented to create geophysical models before and after CO2 injection. Virtual VSP-FWI monitoring experiment is then implemented on the models. In parallel with this, simple linear equations to estimate CO2-saturation and pressure-buildup are derived. Inverted P- and S-wave velocities through the VSP-FWI are found to be highly accurate, and used in the derived equation. As a result the saturation change and reduction of differential pressure are estimated consistently with the values after reservoir simulation. This result indicates that CO2-saturation and pressure-buildup can be differentiated around the well, if both P- and S-wave velocities are accurately inferred by applying VSP-FWI and relevant rock-physics model is known.

Improved algorithm for hyperspectral data dimension determination

Abstract: The correlation between adjacent bands of hyperspectral image data is relatively strong. However, signal coexists with noise and the HySime (hyperspectral signal identification by minimum error) algorithm which is based on the principle of least squares is designed to calculate the estimated noise value and the estimated signal correlation matrix value. The algorithm is effective with accurate noise value but ineffective with estimated noise value obtained from spectral dimension reduction and de-correlation process. This paper proposes an improved HySime algorithm based on noise whitening process. It carries out the noise whitening, instead of removing noise pixel by pixel, process on the original data first, obtains the noise covariance matrix estimated value accurately, and uses the HySime algorithm to calculate the signal correlation matrix value in order to improve the precision of results. With simulated as well as real data experiments in this paper, results show that: firstly, the improved HySime algorithm are more accurate and stable than the original HySime algorithm; secondly, the improved HySime algorithm results have better consistency under the different conditions compared with the classic noise subspace projection algorithm (NSP); finally, the improved HySime algorithm improves the adaptability of non-white image noise with noise whitening process.

Comparison of water extraction methods in Tibet based on GF-1 data.

Abstract: In this study, we compared four different water extraction methods with GF-1 data according to different water types in Tibet, including Support Vector Machine (SVM), Principal Component Analysis (PCA), Decision Tree Classifier based on False Normalized Difference Water Index (FNDWI-DTC), and PCA-SVM. The results show that all of the four methods can extract large area water body, but only SVM and PCA-SVM can obtain satisfying extraction results for small size water body. The methods were evaluated by both overall accuracy (OAA) and Kappa coefficient (KC). The OAA of PCA-SVM, SVM, FNDWI-DTC, PCA are 96.68%, 94.23%, 93.99%, 93.01%, and the KCs are 0.9308, 0.8995, 0.8962, 0.8842, respectively, in consistent with visual inspection. In summary, SVM is better for narrow rivers extraction and PCA-SVM is suitable for water extraction of various types. As for dark blue lakes, the methods using PCA can extract more quickly and accurately.

Comparison of inversion accuracy of soil copper content from vegetation indices under different spectral resolution.

Abstract: Remote sensing inversion of heavy metal in vegetation leaves is generally based on the physiological characteristics of vegetation spectrum under heavy metal stress, and empirical models with vegetation indices are established to inverse the heavy metal content of vegetation leaves. However, the research of inversion of heavy metal content in vegetation-covered soil is still rare. In this study, Pulang is chosen as study area. The regression model of a typical heavy metal element, copper (Cu), is established with vegetation indices. We mainly investigate the inversion accuracies of Cu element in vegetation-covered soil by different vegetation indices according to specific spectral resolutions of ASD (Analytical Spectral Device) and Hyperion data. The inversion results of soil copper content in the vegetation-covered area shows a good accuracy, and the vegetation indices under ASD spectral resolution correspond to better results.