Calibration of P/S amplitude ratios for seismic events in Xinjiang and its adjacent areas based on a Bayesian Kriging method

Correction maps of P/S amplitude ratios for seismic events distributed in Xinjiang, China and its adjacent areas were established using a Bayesian Kriging method for the two seismic stations WMQ and MAK. The relationship between correction maps and variations of along-path features was analyzed and the validity of applying the correction maps to improve performances of P/S discriminants for seismic discrimination was investigated. Results show that obtained correction maps can generally reflect event-station path effects upon corresponding P/S discriminants; and the correction of these effects could further reduce scatters of distance-corrected P/S measurements within earthquake and explosion populations as well as improve their discriminating performances if path effects are a significant factor of such scatters. For example, as corresponding Kriging correction map was applied, the misidentification rate of earthquakes by Pn（2-4 Hz）/Lg（2-4 Hz） at MAK was reduced from 16.3% to 5.2%.

基于XGBoost算法的v_(P)/v_(S)预测及其在储层检测中的应用

鄂尔多斯盆地碳酸盐岩地层蕴含着丰富的油气资源。在勘探实践中发现,大牛地气田马家沟组断层发育、断距小,类型多样且成因复杂,给勘探、开发带来了较多挑战。为了应对这些挑战,提高储层预测的精度变得至关重要。在分析大牛地气田敏感弹性参数的基础上,建立地震属性与储层纵横波速度比(v_(P)/v_(S))的关系,提出一种基于XGBoost算法的地震多属性v_(P)/v_(S)预测方法。为了进一步提升XGBoost算法的预测精度和泛化能力,采用贝叶斯算法对XGBoost算法的超参数进行优化,从而找到最佳的超参数组合,以确保模型在训练集和测试集上的性能均能得到提升。将XGBoost算法应用于Marmousi 2模型进行横波速度预测,预测值与实际值相关系数超过0.88,而均方误差、平均绝对百分比误差分别低于6.55×10^(-7)和4%,验证了该方法的准确性和可靠性。在鄂尔多斯盆地大牛地气田,应用该方法获得的v_(P)/v_(S)成功识别出含气储层,结果与实际钻井数据一致。理论模型和实际数据应用结果表明,XGBoost作为一种强大的机器学习算法预测精度较高,为直接由叠后地震属性预测v_(P)/v_(S)提供了一种有效的途径。

A new method of testing pile using dynamic P-S-curve made by amplitude of wave train

A new method of detecting the vertical bearing capacity for single-pile with high strain is discussed in this paper. A heavy hammer or a small type of rocket is used to strike the pile top and the detectors are used to record vibra- tion graphs. An expression of higher degree of strain (deformation force) is introduced. It is testified theoretically that the displacement, velocity and acceleration cannot be obtained by simple integral acceleration and differential velocity when long displacement and high strain exist, namely when the pile phase generates a whole slip relative to the soil body. That is to say that there are non-linear relations between them. It is educed accordingly that the force P and displacement S are calculated from the amplitude of wave train and (dynamic) P-S curve is drew so as to determine the yield points. Further, a method of determining the vertical bearing capacity for single-pile is dis- cussed. A static load test is utilized to check the result of dynamic test and determine the correlative constants of dynamic-static P(Q)-S curve.

Frequency-dependent attenuation of P and S waves in Yunnan region

We analyzed digital seismogram data of 5668 earthquakes that occurred in Yunnan region between July of 1999 and December of 2003. Among the 22 seismic stations, six ones, namely Baoshan, Yongsheng, Lijiang, Heqing, Yimen, and Luquan, were selected and their attenuations of P and S waves were measured by using the extended coda-normalization method. The six stations were classified into three regions according to their location, that is, Baoshan area, Yongsheng-Lijiang-Heqing (YLH) area and Luquan-Yimen (LY) area. The values of QS-1 and QP-1 are expressed as QS-1=0.00867 f-0.86, QP-1=0.01155 f-0.93, QS-1=0.01824 f-0.92, QP-1=0.02288 f-0.92, and QS-1=0.01647 f-0.91, QP-1=0.02826 f-0.97 in Baoshan, YLH, LY areas respectively. The attenuation of YLH, LY are closer to each other, however, Baoshan area is apparently lower. Comparing attenuation in the three areas with other areas of the world using the same method, it is suggested that the attenuations of P and S waves in YLH and LY areas are close to Kanto of Japan, but much higher than southeast of South Korea. The QS-1 and QP-1 in Baoshan area are slightly higher than southeastern South Korea. Furthermore, the results indicate that our QS-1 in Yunnan area is close to others by analyzing the coda attenuation.

CFD-Based Load Calculation Method for Monopile Support Configuration of Offshore Wind Turbine

An unsteady load calculation method for the support configuration of a monopile-supported offshore wind turbine is developed based on the Fluent software platform.Firstly,the water wave is generated by imposing the inlet boundary conditions according to the exact potential flow solution.Then the wave evolution is simulated by solving the unsteady incompressible Navier-Stokes(N-S)equations coupled with the volume of fluid method.For the small amplitude wave with reasonable wave parameters,the numerical wave result agrees well with that of the given wave model.Finally,a monopile support configuration is introduced and a CFD-based load calculation method is established to accurately calculate the unsteady load under the combined action of wave and wind.The computed unsteady wave load on a small-size monopile support located in the small amplitude wave flow coincides with that of the Morison formula.The load calculations are also performed on a large-size monopile support and a monopile-supported offshore wind turbine under the combined action of small amplitude wave and wind.

v_p/v_s ESTIMATION IN TIBETAN CRUST FROM INVERSION OF SURFACE WAVE DISPERSIONS

We estimated crustal v p/ v s ratio of Tibetan Plateau by combined inversion of Love and Rayleigh wave dispersion data. It is developed by us that the joint inversion methods using both Love and Rayleigh wave dispersion data. Thickness and S\|wave velocity of each sub layer are taken from Love wave dispersion data, then P\|wave velocity structure was deduced using Rayleigh wave dispersion data. Densities of sub layers were estimated by the empirical relationships between seismic velocity and rock density. Having S\| and P\|wave velocities, v p/ v s ratio is calculated for each sub layer. Six sub layers in crust of Tibetan Plateau has been identified, which are 0～8km, 8～30km, 30～40km, 40～62km, 62～68km and 68～75km respectively. The S\|wave velocity structure of the Plateau is 3 13, 3 32, 3 15, 3 92, 3 45 and 3 87 km/s for each sub layer; and P\|wave velocities are 6 00, 6 10, 5 72, 6 35, 6 78 and 6 64km/s respectively v p/ v s ratios in sub layers are 1 92, 1 84, 1 82, 1 62, 1 96 and 1 72; and corresponding Poisson ratios are 0 31, 0 29, 0 28, 0 19, 0 32 and 0 24. Our result on Poisson ratios of Tibetan crust was supported by seismic waveform modelling by Rodgers and Schwartz (1998).

Applicability of P/S amplitude ratios for the discrimination of low magnitude seismic events

Applicability of regional P/S amplitude ratios for the discrimination of low-magnitude seismic events was tested and proved using earthquakes and explosions in Central Asia. Results obtained show that regional P/S amplitude ratios which may discriminate medium or large magnitude events well, are also applicable to low magnitude events Their performances for low magnitude events are almost as good as that for medium or large events. Statistical comparisons based on 25 P/S discriminate from the four seismic stations WMQ, BLK, MUL and MAK showed that the average misclassification rate for low-magnitude seismic events averagely was only 2 percent higher than that for medium and large magnitude seismic events.

Inversion of waveforms from Xiangtang borehole seismic array for soil dynamic property

In order to understand the site soil response of the Xiangtang borehole seismic array under real strong ground motion, reveal the site response, verify the technique of borehole exploration, and improve the precision of in-situ test and laboratory test, this paper presents a new approach, which is composed of two methods. One is the layered site seismic response method, whose layer transform matrix is always real. The other is a global-local optimization technique, which uses genetic algorithm （GA）-simplex method. An inversion of multi-component waveforms of P, SV and SH wave is carried out simultaneously. By inverting the records of three moderate and small earthquakes obtained from the Xiangtang borehole array （2^#） site, the soil dynamic characteristic parameters, including P velocity, damping ratio and frequency-dependent coefficient b, which has not been given in previous literatures, are calculated. The results show that the soil S wave velocity of the Xiangtang 2^# borehole is generally greater than that obtained from the 1994 in-situ test, and is close to the velocity of the 3^# borehole, which is more than 200 m away from the 2^# borehole. Meanwhile, perceptible soil nonlinear behavior under peak ground motion of about 60×10^-2 m/s^2 is detected by the inversion analysis. The presented method can be used for studying the soil response of other borehole array sites.

应用L_(p)拟范数稀疏约束的纵横波速比直接反演

纵横波速比(vP/vS)是识别气藏、描述储层特征和判别岩性的重要解释工具。目前主要是通过反射系数近似方程反演得到纵、横波速度,再进一步计算纵横波速比,但是这种间接计算方法会产生累积误差。为了直接从叠前地震数据反演纵横波速比,文中提出了一种新的广义弹性阻抗方程,再进一步推导出一个与纵横波速比、纵波速度、密度相关的纵波反射系数近似方程。为了得到精度较高的反演结果,基于推导出的反射系数近似方程,提出一种基于Lp拟范数稀疏约束的叠前地震反演方法,并通过交替方向乘子算法求解。将提出的直接反演方法应用于理论模型和实际数据,并与间接反演方法相对比,结果表明该直接反演方法的反演结果精度较高,对含气储层的边界刻画更清晰。

The Q value variations in the preparing pro－cess of rock rupture

In this paper, the 'spectral amplitude ratio method'(SAR) , 'energy method'(EN) and 'coda wave method'(CW) are used to calculate the Q value variations of gneiss in the preparing rupture process. The obtained results show that the variation state of Q values by SAR features the shape of relative stability gradual increment to the maximum then decrement and final rupture.The variation state of Q values by EN is just contrary to that by SAR,i.e.with the shape of stability decrement increment and final rupture . The varation state of Q values by CW is similar to that by EN, its main frequency features the shape of relatively high value decrement to the minimum increment and final rupture.But to the high frequency (higher than the main frequency),the variation state of Q values features the shape of the stable value increment to the maximum decrement and final rupture.At the same time, the results by coda wave amplitude spectrum show that, when stress reaches 70% of rupture stress, the high frequency component of S wave rapidly reduces( Q c increasing); at the time of impending the main rupture, the main frequency component reduces with a large scale( Q c increasing again), this may be the reason which causes the different variation states of two coda Q values.The result of amplitude spectra of P, S(initial wave) waves also show that with the appearance of microcracks the frequency band of S wave turn to be narrow, the high frequency component is reduced quickly, i.e. the S wave spectra have different variation states with different frequeny components. That is why the Q s obtained by different methods have different variation characteristics.

P/S震相幅值比判据对低震级地震事件的适用性检验

基于中国新疆及中亚地区大量天然地震和地下爆炸,检验了较大震级情况下得到的区域P/S震相幅值比识别判据对低震级地震事件的适用性.分析结果表明,对较大震级地震事件具有较好识别效果的P/S震相幅值比判据对低震级事件同样适用,而且对低震级事件也具有与较大震级事件大致相当的识别效果.据WMQ、BLK、MUL和MAK台的25个识别效果较好的P/S震相幅值比判据统计,大于ML3.5和ML3.5以下地震事件的误识率之差约为2个百分点.

云南地区与频率有关的P波、S波衰减研究

分析了1999年7月—2003年12月发生在云南地区的由22个地震台站记录的5 668 次地震的数字波形资料,从中选出保山、永胜、丽江、鹤庆、易门和禄劝6个地震台用扩展的 尾波归一化方法计算P波、S波衰减．这6个台分为3个研究区,保山研究区内Q-1s= O．008 67f-0.86,Q-1p=O．011 55f-0.93;永胜、丽江、鹤庆研究区内Q-1s=O．018 24f-0.94,Q-1p =O．022 88f-0.92;禄劝、易门研究区内Q-1s=O．016 47f-0.91,Q-1p=O．028 26f-0.97．后两个 研究区衰减结果比较接近,而保山研究区的P波、S波衰减明显偏低．与全球其它地区采用 同样方法得到的P波、S波衰减结果对比表明:永胜、丽江、鹤庆研究区和禄劝、易门研究区 的P波、S波衰减与日本关东地区很接近,而远高于韩国东南部的衰减;保山研究区的P波、 S波衰减略高于韩国东南部．此外,还与前人得到的云南地区的尾波衰减结果进行了对比分 析,发现本文S波衰减值与他们的结果相近．

VSP技术在小断块油气田开发中的应用

华北某小断块油气田地处繁华城区,因此不能进行地面地震勘探。为此,对位于小断块的X井进行了多方位非零井源距VSP勘探,获得了井周边地区的高分辨率和高信噪比资料。通过标定,准确确定了任北潜山顶面的反射层位,对井周边地区的构造和小断层进行了解释,圈定了位于潜山顶面的主要目的层——二台阶断块的范围和形态。同时,利用VSP纵波资料的“亮点”特征,并以转换波资料作为印证,对二台阶断块进行了含油气分析,经钻探获得了高产油流。

利用克里金技术标定新疆及附近地区P/S震相幅值比及其在地震事件识别中的应用

针对中国的乌鲁木齐台（WMQ）和哈萨克斯坦的马坎奇台（MAK），采用贝叶斯克里金技术建立了新疆及附近地区地震事件的P／S震相幅值比的校正曲面，并分析了校正曲面与地震波传播路径的关系，以及校正曲面对于改善P／S震相幅值比判据识别效果的有效性．分析结果表明，建立的校正曲面基本合理，结合传播路径差异和地震波传播规律，能够较好地解释校正曲面的起伏特征．而且，在传播路径差异较大，使得P／S震相幅值比经震中距校正后离散度仍然较高的情况下，利用校正曲面修正P／S震相幅值比，可以进一步降低其离散度，从而改善判据的识别效果．MAK台lg[Pn（2～4Hz）／Lg（2～4Hz）]校正曲面修正后，对天然地震的误识率由16．3％下降为5．2％．

一种地震P波和S波初至时间自动拾取的新方法

地震P波、S波初至时间的拾取是地震波分析的一项基础性工作.本文提出了一种新的地震波初至时间自动拾取的方法:首先,把地震波的三分量时程曲线变换为一组空间向的能量变化率时程曲线;然后对能量变化率时程曲线进行STA/LTA(Short Time Average/Long Time Average,短时间的均值/长时间的均值)处理,拾取地震P波和S波的大致初至时间;最后提出采用一种二次方自回归模型对初至附近的能量变化率曲线进行二次方自回归处理,精确拾取出P波和S波的初至时间.本文采用了10组芦山地震的记录数据和150组汶川地震的记录数据对此方法的可靠性进行了检验.以人工拾取结果为参考,此方法具有很高的准确率和稳定性,同时,相比于常用的STA/LTA方法和AIC(Akaike Information Criterion,Akaike信息准则)方法,此方法在计算时间效率方面稍微逊色,但是对S波初至时间的拾取精度和可靠性更高.此方法丰富了地震P波、S波初至时间的自动拾取方法.

基于时频分析的微震P波和S波到时联合拾取方法

微震信号到时的精确拾取是震源定位的重要前提,准确获取微震信号P波、S波到时具有重要理论意义。基于时频分析原理与到时拾取原理,提出了基于时频分析的下山比较法。该方法的时频分析原理通过语谱图、功率密度谱图、连续两次FIR带通滤波获取了背景噪声的位置和规律、P波和S波初至前后微震信号的频率、振幅、能量变化以及光滑且利于迭代平均值比较的波形。该方法的到时拾取原理通过将全子波振幅的数学期望设置为阈值,并遵循P波和S波功率大小、到达先后、波形重叠三大关系迭代比较微震信号子波振幅,从而获得P波精确到时和S波峰值到时。利用模型试验比较了该方法较改进长短时窗(STA/LTA)方法的优越性,并在工程实例中获得验证。结果表明:该方法对比改进STA/LTA方法,前者可同时拾取P波精确到时与S波峰值到时而后者只能拾取P波精确到时,前者P波平均时差、标准差分别为后者的6.18‰、3.98‰,前者单次拾取所需平均计算时间、标准差分别为后者的43.99%、10.54%,前者到时拾取失败比例为0,而后者为15.63%。

腾冲全新世火山区P波和S波速度及其比值

9个发生于观测台网区域上地壳内的地震 ,用P波到时定位 ,从Tp～Ts -p图得出高Vp Vs值 ,显示了低速S波存在的信息。在资料有限情况下 ,假设震中距不变 ,反演震源深度 ,发震时 ,Vp和Vs ,得出Vp =5 90km s ,Vs =3 0 4km s ,Vp Vs =2 94。Vp比区域的同深度平均P波速度 6 0km s低 1 7% ,Vs比按弹性介质的S波速度 =Vp 1 732低 12 4%。这种低速结果符合富含液性物质介质的性质 ,在探测火山区内存在部分熔融岩石或岩浆囊有重要参考价值。

P－SV转换波的一种处理方法─叠前抽道集法

本文利用纵波和横波的迭加速度资料来计算Ｐ－ＳＶ波勘探中转换点的近似位置。再按转换点对Ｐ－ＳＶ波重新抽道集，得到可与反射资料ＣＭＰ道集相兼容的时间剖面图。利用理论模型对上述方法进行了可靠性检验，并用该方法对实际资料作了处理。同时还得到了实际资料的Ｐ波和Ｐ－ＳＶ波的彩色振幅比剖面图。结果表明：采用改进的叠前抽道集法所得到的剖面图具有很好的空间分辨率。

波列振幅PS曲线测桩法

叙述一种新的大应变检测单桩竖向承载力的方法 .用重锤或小型火箭筒冲击桩顶 ,用检波器记录振波图 .引入应变 (变形力 )的高次项 ,从理论上证明当为大位移大应变 ,即桩相对于土体产生整体滑动时 ,位移、速度和加速度则不能经过简单积分加速度和微分速度得到 ,即它们为非线性关系 .由此导出 :通过波列振幅计算力 (P)和位移 (S) ,并作 (动态 )P S曲线、确定屈服点 ,进而阐述确定单桩竖向承载力的方法 ,并利用静载荷试验检验动测结果和确定动静P(Q) S曲线的相关常数 .

以振幅为特征函数拾取P波、S波震相

从以下几个方面对长短时均值比法进行改进:1)使长短时均值比法作为分子的异常项不包含在作为正常项的分母中,突出其表现异常的能力;2)用振幅的4次方作为特征函数,使特征函数体现震相到时特点,拾取震相到时问题转化为寻找特征函数最大值问题;3)仅用竖直向记录拾取P波,用东西、南北两向记录联合拾取S波;4)定义用长短时均值比拾取有效波的第一个峰值为拾取到时阈值的上限,拾取干扰波最大峰值为阈值下限,证实了用振幅4次方作为特征函数拾取震相,其阈值上、下限相差明显,可以定义地震震相到时阈值为阈值下限的2倍;5)明确规定分子的短时间仅仅采用3个记录,当3个记录点包含震相初至的波峰(波谷)和前后次极大值时,长短时均值比一定可得到一个极大值,中间的数据点对应的时刻为震相初至。用改进的方法拾取100个有明显震相的地震记录震相到时,准确度很高。本文方法可以视为是对长短时均值比法的拓展,在确定P波到时阈值后,可以用于地震预警工作中的P波到时的自动拾取。