GBO algorithm for seismic source parameters inversion

The use of geodetic observation data for seismic fault parameters inversion is the research hotspot of geodetic inversion, and it is also the focus of studying the mechanism of earthquake occurrence. Seismic fault parameters inversion has nonlinear characteristics, and the gradient-based optimizer(GBO) has the characteristics of fast convergence speed and falling into local optimum hardly. This paper applies GBO algorithm to simulated earthquakes and real LuShan earthquakes in the nonlinear inversion of the Okada model to obtain the source parameters. The simulated earthquake experiment results show that the algorithm is stable, and the seismic source parameters obtained by GBO are slightly closer to the true value than the multi peak particle swarm optimization(MPSO). In the 2013 LuShan earthquake experiment, the root mean square error between the deformation after forwarding of fault parameters obtained by the introduced GBO algorithm and the surface observation deformation was 3.703 mm, slightly better than 3.708 mm calculated by the MPSO. Moreover, the inversion result of GBO algorithm is better than MPSO algorithm in stability. The above results show that the introduced GBO algorithm has a certain practical application value in seismic fault source parameters inversion.

Study on fault source diagnosis technology and air velocity trans- ducers placement for underground

The current mine safety monitoring system used can only get the air volume change of roadway placed air velocity transducers, as this change is caused by this roadway, or for other roadway, and fault source has one point or more, which be- longs to the problem of fault source diagnosis for ventilation system. Ventilation system fault can be attributed to the variation of air resistance of branch in the entire network. If the changes of air resistance for each branch in ventilation system are ana- lyzed, then it is impossible to place air velocity transducers in every branch. Therefore, the problem of the minimum quantities and location for placing air velocity transducers should be mainly studied. The relationship of air resistance and air volume variation of matrix method has been proposed, which can reflect the variation relationship between the air volume of the branch and air resistance of the relevant branches. Fault roadway range library of ventilation network built to determine fault roadway range will cause air velocity to exceed the limit. Minimum and full coverage of distribution method has been proposed, and the concept of branch coverage degree and impact roadway range library has also been brought forword to get the macro-distribution of air velocity transducers.

Fault Systems and their Control of Deep Gas Accumulations in Xujiaweizi Area

A study of faults and their control of deep gas accumulations has been made on the basis of dividing fault systems in the Xujiaweizi area. The study indicates two sets of fault systems are developed vertically in the Xujiaweizi area, including a lower fault system and an upper fault system. Formed in the period of the Huoshiling Formation to Yingcheng Formation, the lower fault system consists of five fault systems including Xuxi strike-slip extensional fault system, NE-trending extensional fault system, near-EW-trending regulating fault system, Xuzhong strike-slip fault system and Xudong strike-slip fault system. Formed in the period of Qingshankou Formation to Yaojia Formation, the upper fault system was affected mainly by the boundary conditions of the lower fault system, and thus plenty of muiti-directionally distributed dense fault zones were formed in the T2 reflection horizon. The Xuxi fault controlled the formation and distribution of Shahezi coal-measure source rocks, and Xuzhong and Xndong faults controlled the formation and distribution of volcanic reservoirs of Y1 Member and Y3 Member, respectively. In the forming period of the upper fault system, the Xuzhong fault was of successive strong activities and directly connected gas source rock reservoirs and volcanic reservoirs, so it is a strongly-charged direct gas source fault. The volcanic reservoir development zones of good physical properties that may be found near the Xuzhong fault are the favorable target zones for the next exploration of deep gas accumulations in Xujiaweizi area.

Source models for the 2016 Mw6.0 Hutubi earthquake, Xinjiang,China: A possible reverse event

South and north-dipping nodal planes from the U.S. Geological Survey moment tensor solution were used to invert global teleseismic body waves to reveal the source rupture process of the December 8, 2016, Mw6.0 Hutubi earthquake. The results show that a compact pattern is the main feature of this event for only one main slip zone located at the hypocenter for both models, The slip distributions are dominated by a nearly pure-thrust fault, and there is no apparent surface rupture. The inversion revealed that the slip zone extends 10 km along strike and 12 km along dip. The released total seismic moment was about 9.0 -1017 Nm, corresponding to a magnitude of Mw6.0. It is difficult to solve for a best-fit rupture plane due to the sample slip pattern without obvious rupture directivity. This makes the far- field teleseismic data not sensitive enough to determine the fault geometric parameters. The source model of the reverse north-dipping plane fits well with the observed waveforms, and the results of the aftershock relocation outline a trend of north-dipping profiles, indicating the possibility of a reverse event. The inverted normal fault beneath the Qigu fold, interpreted by geological and seismic studies, may be the seismogenic fault for this reverse event.

Complex time－space spreading and focal mechanism of the 1989 Batang earthquake swarm （M_s＝6．7）

On the basis of field observations, the complex time-space spreading pattern and focal mechanism of the 1989Batang earthquake swarm are studied in this paper. The fault motions of the epicenter area are analysed bythe leveling survey before and after strong events. From the given simplified focal mechanical model of theswarm,the process of fracture indicates that swarm strong ruptures are associated with the spreading and thevirgation of the barrier of irregularen en echelon source fault system.

Study on the Cause of Complex Spatial Distribution of the Tangshan Earthquake Sequence

By analyzing higher-accuracy location data of the Tangshan earthquake sequence,a clear distribution pattern of three aftershock belts in the NE,NWW,and NW directions of has been obtained.The analysis reveals three rupture planes of strong events of MS7.8,MS7.1 and MS6.9 in the sequence.It indicates that the complex pattern is closely related to the earthquake source,and the NE-,NWW-and NW-trending regional fault zones,which have been revealed by the research of the pre-seismicity anomaly.In summary,the source is located in the junction of the three fault zones,and the rupture planes of the three strong events located in the source can be regarded as the locked segments on the three fault zones.On these grounds,the paper explains the complexity of the source and epicentral distribution of aftershocks.

Characteristics of Hydrocarbon Accumulation in the Paleozoic Donghetang Formation in the Southwestern Tahe Area

The ancient structure characteristic,correlation of the oil and the hydrocarbon source rock characteristics,hydrocarbon migration trace,types and conditions of traps,migration passages and characteristic of hydrocarbon accumulation are researched in this paper.It is shown through the analysis that two main large tectonic activities after the Early Hercynian orogeny resulted in different tectonic patterns in the study area.Two main hydrocarbon infills occurred in the Donghetang Formation,the first occurred in the Early Hercynian resulting in the ancient hydrocarbon accumulation in the northern Tahe,the second infill was a large amount that occurred in places beneficial for hydrocarbon accumulation,such as structural traps and structural-stratigraphic traps formed in the Early Himalayan orogeny after migration along the faults through source rocks and other passages.Before the earlier period of the Himalayan orogeny,the petroleum mainly migrated to the north,whereas petroleum migrated to the south and southeast because of the structural reverse in the Himalayan orogeny,so the middle and later period of the Himalayan orogeny is the key period for hydrocarbon accumulation.The model of＂oil generation formed early,hydrocarbon accumulation controlled by the faults through source rocks and structures formed late＂is proposed.It is pointed out that the south of the research area is currently the beneficial district for hydrocarbon accumulation, which provides the basis for future petroleum exploration.