图  1   大寨深井台站位置及其记录到的地震分布

黑色圆圈为台站附近的地震分布，黑色实心圆圈为文中反卷积计算用到的地震事件

Figure  1.   Location of the Dazhai borehole station (triangle) and distribution of local earthquakes Circles represent the location of local earthquakes and solid circles are the earthquakes used in this paper.

F₁ : Wuliangshan fault; F₂ : Lancangjiang fault; F₃ : Honghe fault

图  2   大寨井孔结构

两个黑色三角形分别代表位于地表和井下的地震计

Figure  2.   Dazhai borehole columnar diagram

Solid triangles indicate sensors at different depths

图  3   所选取56个地震事件的地表记录与井下记录南北分量(a)和东西分量(b)的傅里叶谱比

Figure  3.   Fourier spectral ratio of local earthquakes using NS (a) and EW (b) components between surface and borehole recordings

图  4   短周期FSS-3DBH地震计的频率特性曲线

Figure  4.   Frequency characteristic curves of the short-period seismometer FSS-3DBH

图  5   M_L3.7地震事件南北向分量的原始波形(a)及其2.0 Hz(b)和1.0 Hz(c)低通滤波结果

Figure  5.   Original waveforms (a) and low-pass filtered waveforms with the cut-off frequencies of 2.0 Hz (b) and 1.0 Hz (c) of the NS component of the M_L3.7 event

Black lines indicate the borehole recordings, and grey lines indicate the surface recordings

图  6   基于均方根误差方法(a)和互相关函数方法(b)得到的不同地震事件南北分裂的最佳旋转角度统计结果

黑色圆圈表示不同事件对应的角度，虚线表示不同角度的中值及均值

Figure  6.   The optimal rotation angles corresponding to NS components of different events by RMS error (a) and cross-correlation (b)

Open circles indicate different angles corresponding to different events, and dashed lines indicate the median and mean value of all rotation angles

图  7   M_L3.7地震事件井下南北分量按照最佳旋转角度旋转前(a)、后(b)的波形对比

Figure  7.   Waveforms before (a) and after (b) rotating the NS component of the M_L3.7 event according to the optimal alignment angle

Black lines indicate the borehole recordings, and grey lines indicate the surface recordings

图  8   井下(a)和地表(b)台站三分量的概率密度函数

Figure  8.   Probability density function of three components from borehole (a) and surface (b) station

图  9   地表和井下台站不同分量的概率密度函数中值差值

Figure  9.   Difference of the median value between probability density function of three-components recorded by surface and borehole stations

图  10   2011年11月9日M_L3.2地震水平分量反卷积波场

(a)不同正则化参数ε下的反卷积波场, 线条颜色由浅变深，表示ε逐渐减小；
(b)不同迭代次数n下的反卷积波场, 线条颜色由深变浅，表示n逐渐增大

Figure  10.   Deconvolution wavefield of the event M_L3.2 with different regularization parameters

(a) Deconvolution variation with regularization parameter ε decreasing from light to dark lines;
(b) Deconvolution variation with Landweber iterations n increasing from dark to light lines

图  11   表 2中事件2(M_L3.2)的原始记录(a)及其相应的反卷积波场(b)

红线表示用于进行反卷积计算的时间窗口，黑色虚线是井下与地表之间相互对称的上行波和下行波

Figure  11.   The deconvolution wavefield (b) from the original records (a) of No.2 event listed in Table 2

The red lines indicate the time window used for deconvolution, and the dashed lines show the up-going wave and down-going wave from bottom to surface

图  12   表 2中地震事件的原始井下记录(a)及其对应的反卷积波场(b)

(a)中红色实线表示用于反卷积计算的时间窗口, (b)中红色虚线分别表示入射波和地表反射波的位置

Figure  12.   Aligned deconvolution wavefield (b) from the original borehole records (a) of all the events listed in Table 2

Red lines indicate the time window used for deconvolution, and vertical dashed red lines indicate the arrivals of incident and surface-reflected waves

图  13   大寨井孔附近的S波(a)和P波(b)速度模型

实心三角形表示两个地震计的深度

Figure  13.   Shear velocity model (a) and P wave velocity (b) around the borehole

Triangle indicates sensors at different depths, and dashed lines indicate the estimated S velocity

图  14   表 2中事件1(M_L3.7)不同深度下切向分量的理论波形(a)、实际波形(b)及其反卷积结果(c)对比

Figure  14.   Synthetic waveforms (a), the observed waveforms (b) and the observed deconvolution (c) of tangential components of No.1 event listed in Table 2