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| 1 | Intrinsic and attenuative dispersion characteristics of direct P-waves in and near the source area of the 1999 MW7.6 Chi-Chi,Taiwan,earth-quake before and after the mainshock显示文摘Based on the measurement of the arrival time of maxima magnitude from band-pass filtering signals which were determined using a new Morlet wavelet multiple-filter method,we develop a method for measuring intrinsic and attenuative dispersion of the first cycle direct P-wave.We determine relative group delays of spectral components of direct P-waves for 984 ray paths from SML and ALS stations of the Taiwan Central Weather Bureau Seismic Network(CWBSN).Using continuous relaxation model,we deduce a new transfer function that relates intrinsic dispersion to attenuation.Based on the genetic algorithm(GA),we put forward a new inversion procedure for determining which is defined the flat part of quality factor Q(ω) spectrum,τ1 and τ2 parameters.The results indicate that 1 The distribution of Qm values versus epicentral distance and depth show that Qm values linearly increase with increasing of epicentral distance and depth,and Qm values is clearly independent of earthquakes magnitude;2 In the different depth ranges,Qm residual show no correlation with variations in epicentral distance.Some significant changes of Qm residual with time is likely caused by pre-seismic stress accumulation,and associated with fluid-filled higher density fractures rock volume in the source area of 1999 Chi-Chi Tai-wan earthquake.We confirm that Qm residual with time anomaly appears about 2.5 years before the Chi-Chi earthquake;3 A comparison of Qm residual for different depth range between SML and ALS stations show that the level of stress has vertical and lateral difference;4 The area near observation station with both anomalously increasing and decreasing averaged Qm residual is likely an unstable environment for future strong earthquake occurrence.This study demonstrates the capability of direct P-waves dispersion for monitoring attenuation characteristics and its state changes of anelastic medium of the Earth at short propagation distance using seismograms recorded from very small events. | Xiqiang Liu Chauhuei Chen Yanwen Zhou Junhao Qu | 2009 | Earthquake Science2009，22，1： | 1 |
| 2 | Synthesis and magnetic properties of Fe_3O_4/helical carbon nanofiber nanocomposites from the catalytic pyrolysis of ferrocene显示文摘High purity Fe3O4 /helical carbon nanofiber composites were obtained on a large scale by the catalytic pyrolysis of ferrocene in the presence of tin powder at 500°C over 12 h. The sizes of Fe 3 O 4 nanoparticles are 35–65 nm in size, and the diameters of the helical carbon nanofibers range from 40–70 nm. The shapes and compositions of the nanocomposites are simply controlled by adjusting the reaction temperatures. On the basis of the obtained experimental results the formation of the helical Fe3O4/carbon nanofiber composites was investigated and discussed. The magnetic hysteresis loop of the products shows ferromagnetic behavior with saturation magnetization (M s ), remanent magnetization (M r ) and coercivity (H c ) values of ca. 29.8 emu/g, 9.6 emu/g and 306.6 Oe, respectively. | ZHANG JunHao WANG JiaoLong WANG HongLiang JIA Liang QU ZhaoKun QIAN YiTai | 2011 | Chinese Science Bulletin2011，56，30： | 0 |
| 3 | Generalization of PhaseNet in Shandong and its application to the Changqing M4.1 earthquake sequence显示文摘Waveforms of seismic events,extracted from January 2019 to December 2021 were used to construct a test dataset to investigate the generalizability of PhaseNet in the Shandong region.The results show that errors in the picking of seismic phases(P-and Swaves)had a broadly normal distribution,mainly concentrated in the ranges of−0.4–0.3 s and−0.4–0.8 s,respectively.These results were compared with those published in the original PhaseNet article and were found to be approximately 0.2–0.4 s larger.PhaseNet had a strong generalizability for P-and S-wave picking for epicentral distances of less than 120 km and 110 km,respectively.However,the phase recall rate decreased rapidly when these distances were exceeded.Furthermore,the generalizability of PhaseNet was essentially unaffected by magnitude.The M4.1 earthquake sequence in Changqing,Shandong province,China,that occurred on February 18,2020,was adopted as a case study.PhaseNet detected more than twice the number of earthquakes in the manually obtained catalog.This further verified that PhaseNet has strong generalizability in the Shandong region,and a high-precision earthquake catalog was constructed.According to these precise positioning results,two earthquake sequences occurred in the study area,and the southern cluster may have been triggered by the northern cluster.The focal mechanism solution,regional stress field,and the location results of the northern earthquake sequence indicated that the seismic force of the earthquake was consistent with the regional stress field. | Zonghui Dai Lianqing Zhou Xuhui Hu Junhao Qu Xia Li | 2023 | Earthquake Science2023，36，3： | 0 |
| 4 | A Review of Aftershock Mechanism Research显示文摘In this paper,research of aftershock mechanisms is reviewed,including heterogeneity of medium and stress,mechanical loading,fluid intrusion and stress corrosion,and ratestate dependence.Previous studies have indicated that the heterogeneity of media and stress is the basic premise of aftershocks generated.From the point view of mechanics,transient creep and afterslip can explain the decay of aftershocks in a short time after a mainshock and the relaxation of stress tends to interpret the characteristics of long-term aftershocks.Fluid intrusion and stress corrosion control the evolution process of the aftershocks under certain conditions.The interaction between the faults perturbed by the mainshock always exists during the aftershock activities.All kinds of models and the theories want to comply with the two basic power-law relationships---the G-R law and Omori law to some extent. | Qu Junhao Jiang Haikun Li Jin Song Jin | 2013 | Earthquake Research in China2013，27，3： | 0 |
| 5 | Shear-wave Splitting in the Crust beneath Shandong and Its Adjacent Area显示文摘Based on the seismic data of near-field source from the Shandong Digital Seismic Network,this study obtained the shear-wave splitting parameters from multiple stations. The results show that dominant directions of polarizations of fast shear-waves reflect the spatial distribution characteristics of tectonic stress in this area,CHD and LIS stations show 2 dominant directions,and reveals that the crustal seismic anisotropy in the Shandong area is constrained by the regional stress background,local failure and structure. | Miao Qingjie Liu Xiqiang Shi Yuyan Qu Junhao Zheng Jianchang Tian Fengdong | 2016 | Earthquake Research in China2016，30，4： | 0 |
| 6 | A Statistical Analysis on Recent Tidal Triggering of the Earthquake in the Tianshan Seismic Zone显示文摘A statistical analysis is done to study the spatio-temporal features of earthquake activity in the Tianshan seismic belt triggered by tide,based on Schusters test. The data we choose is the M L≥2. 0 earthquakes from January 1,2010 to August 31,2012 in eastern Tianshan,and the calculation is on tidal body stress. The results show that the p-value based on the time window smoothing of Schusters test corresponds better with the strong earthquakes in the Tianshan seismic belt,especially for a long time before the November 1,2011 Nilka M S6. 0 earthquake,when the p-value of the Schusters test was always lower than the threshold of 0. 05 for tidal trigger of earthquake,but after the Nilka M S6. 0 earthquake,that value was quickly restored to a high level,which reflects a close relationship between the Nilka M S6. 0 earthquake and the Earth tide. According to the p-value based on the spatial window smoothing of Schusters test,the Nilka M S6. 0 earthquake was at or near the tidal triggering area. Thus we can see from the spatio-temporal results that the Nilka M S6. 0 earthquake was obviously triggered by Earth tide. | Li Jin Jiang Haikun Qu Junhao Huang Yu Gao Chaojun | 2015 | Earthquake Research in China2015，29，2： | 0 |
| 7 | Discussion on the Measurement Method for the Coda Wave Quality Factor显示文摘The Quality factor is the parameter that can be used to describe the energy attenuation on seismic wave. In theory, we can obtain the relationship between the change of the coda wave quality factor with time and the strong earthquake preparation process on the basis of the quality factor of a coda wave in a same ray path. However, in reality the coda wave quality factor measured by different seismic coda waves corresponds to different seismic wave ray paths. The change of the quality factor with time is related to non-elastic characteristics of the medium and the volume of scattering ellipsoid constrained by scattered wave phase fronts, besides the change of regional stress field. This paper discusses the relationship between quality factor, epicenter distance and different lapse time, and then discusses the relationship between quality factor and frequency. Furthermore the determination method of the coda wave quality factor is put forward. The improved determination method of the quality factor, which removes the influence of different earthquakes or propagation depth of scattered waves, may increase measurement precision, thus information pertaining to abnormal changes in quality factor and the relationship between the quality factor and earthquake preparation process can be acquired. | Liu Xiqiang Shi Yuyan Qu Junhao Li Hong Li Bo Zhang Kun | 2009 | Earthquake Research in China2009，23，4： | 0 |
| 8 | Comparative Study of Changes in Stress-drop of the Jinggu MS6.6 and Ludian MS6.5 Earthquake Sequences显示文摘The earthquake stress-drop values of two sequences were accurately calculated after taking away the effects due to regional earthquake anelastic attenuation and station site response,using waveform data and seismic phase data of sequences of the Jinggu M_S6. 6,and Ludian M_S6. 5 earthquakes in Yunnan. These results show that the stress drop with magnitude increases within the scope of this study of magnitude. After eliminating the influence of the magnitude,the average value of stress-drop in the Jinggu sequence is higher than that of the Ludian sequence at the same magnitude range. This may be related to the stress state in different regions. In terms of the changes of time and space of stress-drop,before M_S5. 8 strong aftershock,the stress-drop is 'slowing down-turning up-keeping a high value'after the mainshock,meanwhile,almost all of the abnormally high stress drop value is distributed around the M_S5. 8 strong aftershock, showing that the stress environment in the region was increasing after the mainshock. And after the M_S5. 9 strong aftershock,stress-drop rapidly declines to a relatively stable state,meanwhile,the high value of stress-drop is distributed around the strong aftershock,showing that the regional tectonic stress gets more fully release,its stress environment begins to rapidly decrease.For the Ludian sequence without a strong aftershock occurring,the average value of stress drop is lower than that of the Jinggu earthquake sequence at the same magnitude range,while at the same time,the stress-drop of the aftershock sequence almost hasn't changed much. In the time after the mainshock,combined with the release characteristics of the main energy,the stress in the region is excessively released,the subsequent stress in the region gradually returns to normal. This may be the reason why the activity of Ludianaftershocks significantly was weaker and subsequently there were no strong aftershocks occurred. | Zhou Shaohui Jiang Haikun Qu Junhao | 2017 | Earthquake Research in China2017，31，2： | 0 |
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