近地表Q值测试方法研究进展与展望

准确求取近地表品质因子Q值是构建近地表衰减Q模型、实施反Q滤波处理以提高地震资料分辨率的重要前提。通过对现有近地表品质因子估算方法的梳理，将其初步划分为岩石样本测试Q估算和地层原位测量Q估算两大类。前者依据测试原理的不同可细分为应力-应变法、驻波法和行波法三种；后者按照现场观测技术的不同细分为微测井法、小折射法、大炮初至波法和面波法四种。进一步对不同测试方法的基本原理、应用条件、探测范围、优点与不足等进行对比分析，指出各方法研究和应用中存在的问题。总体而言，岩石样本测试Q估算的测量精度相对较高，但受样本自身局限性及测量频率与地震勘探频率的非一致性等因素影响，测量结果在地震勘探中的实用效果难遂人愿。微测井法和小折射法均可获得有限调查点的较准确Q值，具有较高的纵向分辨率，但难以精准描述Q值横向变化。此外，小折射法还受近地表观测条件限制，地域适应性欠佳。大炮初至直达波法易于估算近地表低降速层Q平均值，能够较好地描述近地表Q值的横向变化，但纵向分辨率不足。初至折射波法无法反映近地表高速层的衰减特性。可控源记录初至波法理论上可获得与小折射法同等精度的Q值纵向分辨率，且具有优于小折射法的横向Q值变化刻画能力。面波法主要应用瑞雷面波，包括来自大炮记录的瑞雷面波信息，其探测深度较小，主要揭示近地表风化层的Q值。此外，受面波信息处理、提取和速度频散曲线求取精度等限制，现有的面波法Q值估算精度有限。井地联合及多源信息融合Q反演应该是未来近地表准确Q值反演和应用研究的主要发展方向。

Progress and outlook of near-surface quality factor Q measurement and inversion

The accurate determination of near-surface quality factor Q is an important basis for constructing near-surface attenuation Q models and implementing inverse Q filtering to improve the seismic resolution.Based on our analysis,the existing near-surface Q-value estimation methods may be divided into two categories:Q-value estimation with rock sample testing and Q-value estimation with stratum in-situ survey data.For the first category there are three approaches:stress-strain,standing wave,and travel wave according to different test principles.For the latter category,there are four methods:uphole survey,shallow first breaks from common-shot-point (CSP),and surface wave method according to different field survey techniques.In this paper we analyze the principles,application conditions,detection ranges,advantages and disadvantages of the methods.The Q value estimation based on rock sample testing has a high accuracy.However,due to the limitations of the sample and the incongruity between the measurement frequency and the seismic frequency,estimated values have lots of limitations in the seismic exploration.Both the uphole survey and the shallow refraction methods can obtain more accurate Q estimations with high vertical resolution,but they can hardly show horizontal Q value changes.The shallow refraction is limited by surface survey conditions.The first breaks method can obtain the average Q value of low velocity layers,and can better describes lateral variations of Q values,but its vertical resolution is insufficient.The first break refraction cannot show attenuation characteristics of near-surface high-velocity layers.The vibroseis seismic first breaks method is not subject to this restriction,it can obtain the same precision vertical resolution as the shallow refraction,and better Q value lateral variations.The surface wave method is mainly based on Rayleigh-wave,including the Rayleigh-wave from CSP records.The detection depth is relatively shallow,which usually reveals weathering layer Q values.Besides,the accuracy of Q estimation of this method is limited by the precision of velocity dispersion curves.So,the development tendency of near-surface Q inversion will be multi-information joint application such as surface and borehole seismic integration in the future.