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首页> 外文期刊>South African Journal of Geology: Being the Transaction of the Geological Society of South African: Syndie die Verhandelinge van die Geologiese Vereniging van Suid-Afrika >Experimental studies of elastic wave velocities and densities in rocks from the Bushveld Complex, South Africa: implications for deep reflection seismic surveys
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Experimental studies of elastic wave velocities and densities in rocks from the Bushveld Complex, South Africa: implications for deep reflection seismic surveys

机译：南非蒲团岩石岩石弹性波速和密度的实验研究：深度反思地震调查的影响

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To provide guidelines for future seismic surveys in the Bushveld Complex, we have conducted laboratory experiments to measure P-wave and S-wave velocities at ultrasonic frequencies on drill-core samples as a function of stress and bulk density. The rock samples include gabbroic, anorthositic, troctolitic and magnetite-olivine rich horizons, as well as granitic sills. Ultrasonic measurements of P- and S-wave velocities were conducted at both atmospheric pressure, and at elevated uniaxial stresses up to 65 MPa (equivalent to depths of 2 km), using 0.5 MHz P- and S-wave transducers. The results show that the seismic velocities tend to increase with increasing olivine or pyroxene content (e.g., Vp ~6.00 km/s for olivine ferrodiorite), and decrease with increasing plagioclase content (e.g., Vp ~4.70 km/s for troctolite). The bulk density and ultrasonic measurements suggest that significant reflection coefficients (RC) occur at some stratigraphic contacts that are readily identifiable in surface exposures (e.g., RC?0.09 for granite-olivine ferrodiorite contact), implying that these horizons, at least in terms of acoustic impedance contrasts, are favourable targets for surface reflection seismic surveys. Our results also suggest that with increasing stress (0 to 20 MPa), seismic wave velocities increase slightly for both anorthosite (Vp~5.5 to 6.0 km/s) and troctolite (Vp~4.80 to 7.20 km/s). The velocities are constant at higher stresses (20 to 65 MPa), which can be attributed to closure of macro- and microcracks at depths of 1.0 to 1.5 km. The observed relationship between seismic velocities, modal mineralogy and stress has particularly important implications (e.g., velocity analysis for seismic processing and time-to-depth conversion of the seismic data) for the design of future long, deep seismic profiles that can be used to constrain the deep structure and connectivity of the western and eastern limbs of the Bushveld Complex at depths.
机译：为了提供BUSHVELD复合体中未来地震调查的指导，我们已经开展了实验室实验，以测量钻孔样品上超声波频率的P波和S波速度，作为应力和散装密度的函数。岩石样品包括Gabbroic，华盛症，脱卵石和磁铁矿 - 橄榄石的富裕的视野，以及花岗岩。使用0.5MHz的P和S波传感器，在大气压下进行P速度的超声波和S波速度的超声测量，并且在高达65MPa（相当于2km的深度）的升高。结果表明，随着橄榄石或氟化辛含量（例如，橄榄石铁摩托岩的VP〜6.00 km / s）的增加，地震速度趋于增加，并随着普通粘接酶含量的增加而降低（例如，用于脱卵石〜4.70mm / s）。堆积密度和超声测量表明，显着的反射系数（RC）发生在一些地层触点上，其在表面曝光中容易识别（例如，RCα09用于花岗岩橄榄石嗜酸性梭菌接触），这意味着这些视野，至少在方面声阻抗对比度，是表面反射地震调查的有利目标。我们的研究结果表明，随着应力（0至20MPa）的增加，岩石速度略有增加（VP〜5.5至6.0 km / s）和塞子（Vp〜4.80至7.20 km / s）。速度在较高的应力（20至65MPa）处是恒定的，这可以归因于宏观和微裂纹的宏观和微裂纹，深度为1.0至1.5公里。所观察到的地震速度，模态矿物学和应力之间的关系具有特别重要的影响（例如，用于抗震处理和地震数据的时间 - 深度转换的速度分析），用于设计的未来长度，深层地震曲线的设计在深度中约束Bushveld综合体的西部和东部肢体的深层结构和连通性。

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