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Performance analysis of a new baseline-based SS-Y extensometer

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geodesy and Geodynamics 2018年第5期9卷 418-423页

作者： Linbin Wu Zhaosheng Nie Key Laboratory of Earthquake Geodesy Institute of SeismologyChina Earthquake Administration

In order to solve the problems in the observation with the SS-Y extensometer, such as background noise and discontinuity of earth tide curve, this paper proposed to improve the stability of the instrument and the smoothness of the earth tide curve by improving the baseline structure of the instrument. In this study, a new φ20*1.2 invar tube was introduced in replacement of the existing φ6 invar rod as the baseline of the instrument and compared with the existing φ6 invar rod on the instrument’s linearity,sensitivity and other indexes. Firstly, the SS-Y extensometers using φ6 invar rod and cp20*1.2 invar tube were tested. Test results were then calculated, and accuracy errors of the instruments based on the two baselines were obtained. Finally, their accuracy errors and earth tide curves were compared. Results showed that, compared with the extensometer based on the existing φ6 invar rod, the extensometer based on the new φ20*1.2 invar tube was superior in performance, with linearity error reducing to 0.495% from 0.937%, sensitivity increasing to 68.65 mV/μm from 65.46 mV/μm, and earth tide curve growing more stable and continuous.

关键词： Invar tube Extensometer Ground deformation Background noise Earth tide

Three-dimensional admittance analysis of lithospheric elastic thickness over the Louisville Ridge

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earthquake Science 2016年第2期29卷 117-125页

作者： Minzhang Hu Hui Li Chongyang Shen Lelin Xing Hongtao Hao Key Laboratory of Earthquake Geodesy Institute of SeismologyChina Earthquake Administration

Using bathymetry and altimetric gravity anomalies, a 1°×9 1° lithospheric effective elastic thickness（Te） model over the Louisville Ridge and its adjacent regions is calculated using the moving window admittance technique. For comparison, three bathymetry models are used： general bathymetric charts of the oceans, SIO V15.1,and BAT_VGG. The results show that BAT_VGG is more suitable for calculating T e than the other two models. T e along the Louisville Ridge was re-evaluated. The southeast of the ridge has a medium Te of 10–20 km, while Te increases dramatically seaward of the Tonga-Kermadec trench as a result of the collision of the Pacific and IndoAustralian plates.

关键词： Three-dimensional admittance analysis Lithospheric effective elastic thickness Bathymetry Gravity Louisville Ridge

Seasonal features of topside scale height based on COSMIC measurements

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geodesy and Geodynamics 2017年第5期8卷 328-334页

作者： Fanfan Su Jian Lin Fuying Zhu Yiyan Zhou Jian Yang Liangchen Hu Key Laboratory of Earthquake Geodesy Institute of SeismologyChina Earthquake Administration

Plasma scale height is an important parameter of topside ionosphere and contains information about ionospheric physics and dynamic. We investigated the seasonal features of vertical scale height with the electron density profiles from COSMIC. We found that vertical scale height around 660 km at middle latitudes generally has larger values in winter than in summer and had similar structures at March Equinox and September Equinox no matter daytime or nighttime. Bands of large vertical scale height appear at night around ±36° magnetic latitude in all seasons except summer for low solar activity, and mostly appear in winter for moderate solar activity. Vertical scale height in the middle latitudes generally has smaller values for moderate solar activity than that for low solar activity around 660 km, and has smaller values in the daytime than at night.

关键词： Scale heightTopside ionosphereCOSMICElectron density

Location correction technique based on mobile communication base station for earthquake population heat map

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geodesy and Geodynamics 2018年第5期9卷 388-397页

作者： Xiaoli Liu Xue Li Xiaolin Chen Zhumei Liu Shengle Li Institute of Seismology China Earthquake Administration Key Laboratory of Earthquake Geodesy China Earthquake Administration

China has mobile phone penetration rate of over 96.2%.Mobile phone has become the largest Internet terminal for Chinese Internet users.Population geographic distribution in earthquake zones can be got based on mobile phone positioning and map matching.For reducing earthquake black-box stage,we propose a real-time collection,correction and schedule algorithm of population position data by four stream processing environments(Redis,Hbase,Kafka,and Spark Streaming)in this paper.For labeling precisely population geographic distribution on the network map,matching of population geographic coordinates and map coordinates are optimized by sample comparison based on location data of mobile communication base stations and prefecture level cities.The test result shows the proposed system is high efficient and can rapidly respond to any emerging parallel tasks during the earthquake.A high-precision heat map of affected population can be produced and published on-line within 2 min after the devastating earthquake happened.

关键词： earthquake emergency Location-based service Mobile communication base station Big data technology

Mapping coalmine goaf using transient electromagnetic method and high density resistivity method in Ordos City, China

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geodesy and Geodynamics 2016年第5期7卷 340-347页

作者： Guiju Wu Guangliang Yang Hongbo Tan The Key Laboratory of Earthquake Geodesy Institute of Seismology China Earthquake Administration

The research about subsurface characteristics by using transient electromagnetic method（TEM） and high density resistivity method（HDRM） were already conducted in Ordos. The objective of this research is to detect coalmine goaf areas based on rock resistivity. The data processing using wavelet transform, three point smoothing, RES2 DINV and Maxwell processing software to obtain 2D resistivity structure. The results showed that the layers with maximum resistivity values（30e33 U m on Line 1, 30e31 U m on Line 2, 32e40 U m on Line3） are founded at station 1e7, and 14e20 on Line 1,13e18 on Line 2, and 8e13 and 16e20 on Line 3 which is predicted as goaf layer, and the minimum resistivity values（20e26 U m of TEM, 45e75 U m of HDRM） at the other layers. This resistivity difference was caused by the geology and characteristics of the study area which is located close by the cleugh with rich coal, so the goaf area distinguishable with aquifer layer and coal seam. The results were also significant accidents and serious destruction of ecological environment.

关键词： Transient electromagnetic method High density resistivity method Coalmine goaf areas Geotechnical Electrical

Active tectonic deformation around the Tarim Basin inferred from dense GPS measurements

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geodesy and Geodynamics 2020年第6期11卷 418-425页

作者： Dongzhen Wang Bin Zhao Jiansheng Yu Kai Tan Key Laboratory of Earthquake Geodesy Institute of SeismologyChina Earthquake AdministrationWuhan430071China

The surrounding area of the Tarim Basin is featured by active tectonic deformation and intense seismic activity.The study of the crustal deformation characteristics of this area will help revealing the role of the Tarim Basin in the crustal evolution.In order to accurately obtain the deformation characteristics of this area,we firstly obtained the highly detailed and accurate three-dimensional(3D)crustal deformation velocities of the Tarim Basin and its surrounding areas through high-precision processing of existing Global Positioning System(GPS)data.Thereafter,the slip rate and strain rate fields of the main faults in the region were calculated based on the updated velocity results.The strain rate of the Altyn Tagh fault is dominated by shear strain and the strike slip rate is 8-10 mm/yr.The strain rate between the Tien Shan and Tarim Basin is dominated by extrusion strain,and the extrusion rate is 4-6 mm/yr.In addition to the large shear strain,there is also a certain tensile strain in the Tibetan Plateau.Geodetic results show that the main driving force for the deformation of the Tien Shan is the northward thrust of the Tarim Basin.The relative movement mode between the Tarim Basin and Tibetan Plateau mainly comprises the strike slip movement along the strike direction of the Altyn Tagh fault,with a small extrusion deformation.Therefore,the Tarim Basin has little influence on the northesouth shortening deformation of the Tibetan Plateau.

关键词： Tarim Basin Velocity field Strain rate Slip rate Crustal deformation

Ionospheric disturbances associated with the 2015 M7.8 Nepal earthquake

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geodesy and Geodynamics 2017年第4期8卷 221-228页

作者： Yiyan Zhou Jian Yang Fuying Zhu Fanfan Su Liangchen Hu Wenbo Zhai Institute of Seismology China Earthquake Administration Key Laboratory of Earthquake Geodesy China Earthquake Administration

Based on the total electron content （TEC） derived from Global Positioning System （GPS） observations of the Crustal Movement Observation Network of China （CMONOC） and the Global Ionosphere Map （GIM） from the Center for Orbit Determination in Europe （CODE）, we detected and analyzed the ionospheric variations during the 2015 M7.8 Nepal earthquake （including the pre-earthquake ionospheric anomalies and coseismic ionospheric disturbances （CIDs） following the main shock）. The analysis of vertical total electron content （VTEC） time series shows that the large-scale ionospheric anomalies appeared near the epicenter two days prior to the earthquake. Moreover, the pre-earthcluake ionospheric anomalies were also observed in the geomagnetically conjugated region. In view of solar-terrestrial environment, the pre-earthquake ionospheric anomalies could be associated with the Nepal earthquake. In addition, we also detected the CIDs through the high-frequency GPS observation stations. The CIDs had obvious oscillated waveforms with the peak-to-peak disturbance amplitudes of about I TECu and 0.4 TECu, which propagated approximately with the horizontal velocities of 877 ±75 m/s and 319 ± 30 m/s, respectively. The former is triggered directly by the acoustic waves which originated from the energy release of the earthquake near the epicenter, while the latter could be stimulated by the acoustic-gravity waves from the partial transformation of the acoustic waves.

关键词： GPS TEC M7.8 Nepal earthquake Pre-earthquake ionospheric anomalies CID

Offset measurements along active faults based on the structure from motion method——A case study of Gebiling in the Xorkoli section of the Altyn Tagh Fault

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geodesy and Geodynamics 2020年第5期11卷 358-366页

作者： Baosong Xiong Xue Li Key Laboratory of Earthquake Geodesy Institute of SeismologyChina Earthquake AdministrationWuhan430071China

This study reconstructs high-precision three-dimensional(3 D) surface models using aerial imagery derived from unmanned aerial vehicles(UAVs) with the structure from motion(SfM) method. By combining automatic extraction and manual visual interpretation, the geometry of the active tectonics and offset channels along the fault is obtained. The offsets, caused by the motion of active tectonics, are measured via the retrodeformation of geomorphologic markers. This paper takes the tectonic geomorphology of Gebiling in the Xorkoli section of the Altyn Tagh fault as a case study. After the construction of 3 D surface models using the UAV images and the SfM method, a data set of more than 200 offsets is obtained. The results indicate that 11 paleoearthquakes may have ruptured along the Gebiling section of the Altyn-Tagh fault.

关键词： fault tectonics tectonic

The influence of observation environment on background noise level of gPhone gravimeter

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geodesy and Geodynamics 2017年第6期8卷 443-447页

作者： Xiaotong Zhang Ying Jiang Kun Zhang Xinlin Zhang Institute of Seismology China Earthquake Administration Key Laboratory of Earthquake Geodesy China Earthquake Administration

Based on the observations of 36 gPhone gravimeters in 2015, the background noise levels in the seismic frequency band（200-600 s） and sub-seismic band（1-6 h） are calculated. The differences in the PSD（power spectrum density） of each band of gPhone gravimetric gauges in different surrounding environments were analyzed and compared with Peterson＇s NLNM（new low-noise model） which is derived from the envelope at the power spectrum density of 75 seismograph stations around the world. The results showed that： the influence of station type on the noise magnitude of gPhone gravimeter is very small; The seismic band noise magnitude（hereinafter referred to as SNM） and the sub-seismic band noise magnitude（hereinafter referred to as SSNM） in the coastal gPhone gravimeter are higher than those of inland stations. Although the local hydrological change has a great influence on the gravity observation, the rainfall is not directly relative to the noise magnitude of the instrument. Except 3 coastal stations, the eight stations which had the highest amplitudes in the SNM were located near the seismic belt. This indicates that the SNM of the gPhone Gravimeter may reflect some seismic information.Compared with the NLNM model, the PSD of the gPhone gravimeter is lower than the NLNM model in the long period band（〈3×10^（-5）Hz）, indicating that the gPhone gravimeter is more suitable for detecting long-period signals（〉10 h） than the seismometer.

关键词： gPhone gravimeter Background noise level NLNM Observation environment