Ice-Shelf Densities from a Comparison of Radio Echo and Seismic Soundings
Ice-Shelf Densities from a Comparison of Radio Echo and Seismic Soundings
复制标题
无线电回波和地震探测比较的冰架密度
作者：
C. Doake
1981年1月，用无线电回波法和地震反射法对横跨乔治六世冰架的40公里线进行了测深。由于无线电波和地震波的速度以不同的方式随冰密度的变化而变化，因此通过两种方法对传播时间进行精确比较，就可以计算出冰架的平均密度。在23个地震台站中，有22个台站记录到了来自冰架底部的可识别回波。在厚度从200米到350米不等的冰层中实现了连续的无线电回波剖面。计算得到的平均密度分为两组，夏季融水频繁泛滥地区的平均密度约为0.915 Mg m−3，而干旱地区的平均密度约为0.884 Mg m−3。除此之外，平均密度随位置的变化没有明显的系统变化。探测大约是沿着冰架上的一条流线进行的。在模拟冰架变形时，很难考虑冰密度随深度和位置的变化。例如，表面应变率的测量值在某些情况下可能需要校正由于雪的可压缩性而产生的影响。
A 40 km line across George VI Ice Shelf was sounded in January 1981 by both radio echo and seismic reflection methods. Because the velocities of radio and seismic waves vary with ice density in different ways, an accurate comparison of travel times from the two methods allowed the average density of the ice shelf to be calculated. A distinguishable echo from the base of the ice shelf was recorded at 22 out of 23 seismic stations. Continuous radio echo profiling was achieved in ice varying in thickness from about 200 to 350 m. The calculated mean densities fell into two groups, In an area where summer meltwater frequently floods the surface the average densities were around 0.915 Mg m−3, while in the drier areas the average densities were around 0.884 Mg m−3. Apart from this division, there was no apparent systematic variation of average density with position. The sounding was carried out approximately along a flowline on the ice shelf. The variation of ice density with depth and position is difficult to allow for when modelling the deformation of ice shelves. Measured values of surface strain-rate, for example, may in some circumstances need to be corrected for effects due to the compressibility of snow.