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| 1 | Crustal velocity structure of the Shaowu-Nanping-Pingtan transect through Fujian from deep seismic sounding-tectonic implications显示文摘The Shaowu-Nanping-Pingtan deep seismic sounding profile is located in northern Fujian Province. High-quality seismic sounding data were acquired by five large explosive blasts received by 133 digital seismic instruments along the profile. Based on seismic facies analysis and travel-time picking on shot record sections, a model of the velocity structure of upper crust was developed by finite-difference tomography of the first breaks; the 2-D P-wave velocity structure and tectonic characteristics of the crust were interpreted further by fitting of waveforms and seismic travel times. The results show that the top of the crystalline basement is buried at depths of 2.0–4.0 km, with the deepest buried up to 4.0 km within the Fuzhou Basin. The Moho interface was found to be deeper in the west and shallower in the east(i.e., 30.0 km near the coast, increasing to 33.0 km northwestward). The lower crust on the east side of the Zhenghe-Haifeng Fault Zone has a smoothly varying gradient structure, whereas on the west side it has two distinct layers with a boundary between those layers at a depth of 23 km. Seismic velocities on the west side are generally lower than on the east side; a low velocity layer is observed with a lowest speed of 6.25 km/s at a depth of 22 km on the west side, which may consist of partially molten material. The Zhenghe-Haifeng Fault is a deep crustal fault, and should be a channel for deep material upwelling; it has a direct relationship with multiple stages of continental tectonic movements in Southern China and with multiple magmatic events that started in the Proterozoic and ended in the of late Tertiary in Fujian. | LI Pei JIN Xin WANG ShanXiong CAI HuiTeng | 2015 | Science China Earth Sciences2015，58，12： | 9 |
| 2 | An Experimental Study on Optimization of Large-volume Airgun Source Excitation Conditions in a Reservoir显示文摘Through manual pickup of seismic phases,the number of recording stations,the farthest observation distance of station and received energy are determined,then optimal operating condition processing software is developed to evaluate the excitation effect of operating conditions. The optimal operating conditions in the Mianhuatan Reservoir are determined using this software. They are: optimal water depth 25 m,airgun array sink depth 9m and airgun array size 7m × 7m. At the same time,accumulative stacking results for every 10 times are analyzed for 300 fixed-point excitations. It is concluded that the excitation effect shows a rapidly rising trend at 10 to 90 times stacking,a slowly rising trend at 100 to 150 times stacking,a rapidly rising trend at 160 to 240 times stacking,and a slowly rising trend at 250 to 300 times stacking. As the number of stacking increases,the propagation distance and the number of recording stations also increase gradually. | Chen Huifang Lin Binhua Jin Xing Wu Lihua Cai Huiteng | 2016 | Earthquake Research in China2016，30，3： | 4 |
| 3 | Signal Detection of Large Volume Airgun Source Excitation in the Fixed Field of the Yangtze River显示文摘As this is the first time a large volume airgun has been excited in the 'Yangtse River Geoscience Project',it is necessary to study the time-frequency characteristic based on the linear stacked seismic data from records from portable stations near the fixed fields and seismic stations. Airgun signal propagation distances were detected using stacked seismic data to analyze the environmental impact on signal propagation distance. The results showed that:( 1) the airgun signal produced by bubble pulses,pressure pulses and the surface wave can be received by a portable station near the fixed field;( 2) the dominant frequency of a bubble at 5Hz or so can be received by both near-field stations and far-field stations,pressure pulses rapidly weaken and the dominant frequency bands get narrower as epicentral distance increases;( 3) the longest spread distance of signal is 260 km,the nearest is 180 km,and the signal can travel further in the evening. | Xu Jiajun Cai Huiteng Jin Xing Wang Shanxiong Xia Ji Li Pei | 2016 | Earthquake Research in China2016，30，3： | 4 |
| 4 | Some Thoughts on the Earthquake Science Experimental Site——The Underground Cloud Map显示文摘The Western Yunnan Earthquake Predication Test Site set up jointly by the China Earthquake Administration,the National Science Foundation Commission of America,and United States Geological Survey has played an important role in development of early earthquake research work in China. Due to various objective reasons, most of the predicted targets in the earthquake prediction test site have not been achieved,and the development has been hindered. In recent years, the experiment site has been reconsidered,and renamed the 'Earthquake Science Experimental Site'. Combined with the current development of seismology and the practical needs of disaster prevention and mitigation,we propose adding the 'Underground Cloud Map'as the new direction of the experimental site. Using highly repeatable, environmentally friendly and safe airgun sources,we could send constant seismic signals,which realizes continuous monitoring of subsurface velocity changes. Utilizing the high-resolution 3-D crustal structure from ambient noise tomography,we could obtain 4-D (3-D space+1-D time) images of subsurface structures, which we termed the 'Underground Cloud Map'. The'Underground Cloud Map' can reflect underground velocity and stress changes,providing new means for the earthquake monitoring forecast nationwide,which promotes the conversion of experience-based earthquake prediction to physics-based prediction. | CHEN Yong XU Yihe CAI Huiteng LI Wen | 2019 | Earthquake Research in China2019，33，1： | 1 |
| 5 | Experiments on Exploration of Shallow Fine Structures and the Construction of the 1-D Velocity Model in the Pingtan Island,Fujian显示文摘112 short-period seismographs were set up in the 400 km^2 area of Pingtan Island and its surrounding areas in Fujian.The combined observations of the airgun source and ambient noise source were carried out using a dense array to receive the 387 airgun signals excited around the island and one month of continuous ambient noise recording.The 1-D P-wave and S-wave shallow velocity model of Pingtan Island is obtained by the inversion of the airgun body wave’s first arrival time data,and the reliability of the velocity model is verified by using the surface wave phase velocity dispersion curve,which can provide initial model for subsequent 3-D imaging.The experimental results show that this experiment is a successful demonstration of local scale green non-destructive detection,which can provide basic data for shallow surface structure research and strong vibration simulation of the Pingtan Island. | GUO Yang XU Jiajun LIN Chen JIN Xing YAO Huajian YANG Hongfeng CAI Huiteng | 2019 | Earthquake Research in China2019，33，2： | 1 |
| 6 | The Time-frequency Characteristic of a Large Volume Airgun Source Wavelet and Its Influencing Factors显示文摘Through analyzing the near-field hydrophone records of the airgun experiment in the Jiemian reservoir,Fujian,we study the time-frequency characteristic of airgun source wavelet and the influence of gun depth and firing pressure,and explain the process of bubble oscillation based on the Johnson( 1994) bubble model. The data analysis shows that:( 1) Airgun wavelet is composed of primary pulse and bubble pulse. The primary pulse,which is of large amplitude,short duration and wide frequency band,is usually used in shallow exploration. The bubble pulse,which is concentrated in the low-frequency range,is usually used in deep exploration with deep vertical penetration and far horizontal propagation.( 2) The variation of primary pulse amplitude with gun depth is very small,bubble pulse amplitude and the dominant frequency increase,and peak-bubble ratio and bubble period decrease. When the gun depth is 10 m,primary pulse amplitude and peakbubble ratio are maximum,which is suitable for shallow exploration; when gun depth is25 m,bubble pulse amplitude is large, and peak-bubble ratio is minimum, which is suitable for deep exploration.( 3) The primary pulse amplitude,bubble pulse amplitude,peak-bubble ratio,and bubble period increase and the dominant frequency decreases with increased firing pressure. | Xia Ji Jin Xing Cai Huiteng Xu Jiajun | 2016 | Earthquake Research in China2016，30，3： | 0 |
| 7 | Attenuation Characteristics of Earthquake Ground Motion for Large Volume Airgun显示文摘In order to further deepen the understanding of seismic wave propagation characteristics induced by the large volume airgun source,experimental data from multiple fixed excitation points in Fujian Province were used to obtain the equivalent single excitation high signal-to-noise ratio velocity and displacement records through linear stacking and simulation techniques.Then the peak displacements of different epicentral distances were used to calculate the equivalent magnitude of the airgun source excitation at different fixed excitation points so as to establish the attenuation relationship between equivalent magnitude,epicenter distance and velocity peak.Our results show that:①Within 270 km of epicentral distance,for the large-volume airgun’s single shot,the peak velocity range is about 700-4 nm/s,and the peak displacement range is about 200.0-0.2 nm;②The equivalent magnitude of the P-wave from the airgun source with a total capacity of 8,000 in 3 is 0.181-0.760,and the equivalent magnitude of the S-wave is 0.294-0.832.By contrast,the equivalent magnitude of the P-wave from the airgun source with a total capacity of 12,000 in 3 is 0.533-0.896,and the equivalent magnitude of the S-wave is 0.611-0.946.The S-wave energy is greater than the P-wave energy,and the excitation efficiency varies greatly with different excitation environment;③The peak velocity increases with the equivalent magnitude,and decreases with the epicentral distance.The vertical component of the P-wave peak velocity is the largest among those three components,while the S-wave has the smallest vertical component and similar horizontal components.Hence,our research can provide an important basis for the quantitative judgment of the seismic wave propagation distance using the airgun and the design of the observation system in deep exploration or monitoring with airgun. | CAI Huiteng CHEN Yong JIN Xing XU Yihe LI Wen | 2019 | Earthquake Research in China2019，33，4： | 0 |
| 8 | Review of the 2018 Palu Tsunami: Disaster Behavior and Reflections on Disaster Management显示文摘The 2018 Palu M_W7.5 earthquake and tsunami attracted geophysicists' attention for its strike slip focal mechanism and magnitude. We inspected the details of this disaster and discussed its particularity and possible causations. The submarine landslide and special terrain conditions could have contributed to the unusual size of the tsunami. The early warning system and the post disaster response is also reviewed. Efficient social warnings and broadcast systems along with good maintenance is essential. We also found that enhancing publics scientific literacy is the most important way to reduce disaster damage and casualties. Moreover, social conditions and rebuilding difficulties post tsunami are related as reference resources for future disaster management strategies. | HU Jiupeng CHEN Yong LI Wen XU Yihe CAI Huiteng | 2019 | Earthquake Research in China2019，33，1： | 0 |
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