UTEP Source Test 2017

Selecting the appropriate seismic source is important to reach geologicalproject objectives. We compare seismic sources between explosive sources (pentolite and shotgun) and mechanical sources (accelerated weight drop and hammer on plate), focusing on amplitude and frequency. All sources were tested in same geologic environment.. Although this is not an ideal geologic formation for source coupling, it does allow an “apples to apples” comparison. Twenty20 Reftek RT125A seismic recorders withing instruments (4.5 Hz geophones) were laid out in a line with 3-meter station separation. Mechanical sources were tested first to minimize changes in the subsurface related to explosive sources Explosive sources, while yielding higher amplitudes, havebut lower frequency content. The explosions exhibit a higher signal-to-noise ratio, allowing us to recognize seismic energy deeper and farther from the source. Mechanical sources yield higher frequencies allowing better resolution at shallower depths, but have a lower signal-to-noise ratio and lower amplitudes, even with source stacking. We analyze the details of the shot spectra from the different types of sources. A combination of source types can improve data resolution and amplitude, thereby improving imaging potential. However, cost, logistics, and complexities also have a large influence on source selection.

选取合适的震源（seismic source）对达成地质工程目标至关重要。本次实验对比了爆炸震源（explosive sources，包括彭托利特炸药pentolite与霰弹枪震源shotgun）与机械震源（mechanical sources，包括加速下落重锤震源accelerated weight drop与平板锤击震源hammer on plate）的性能表现，重点考察振幅与频率特征。所有震源均在同一地质环境中开展测试。尽管该地质构造并非震源耦合（source coupling）的理想工况，但仍可实现"apples to apples"的严格对等对比。本次实验采用搭载4.5Hz检波器（geophone）的20通道Reftek RT125A地震记录仪，沿直线布设，道间距为3米。为尽量降低爆炸震源对地下介质造成的改变，实验优先测试机械震源。爆炸震源虽可获得更高振幅，但频率成分更低；其信噪比（signal-to-noise ratio）更高，可识别震源更远、更深位置的地震波能量。机械震源的频率更高，可在浅部获得更优的分辨率，但即便采用震源叠加（source stacking）技术，其信噪比与振幅仍相对更低。我们对不同类型震源的炮点频谱细节展开了分析。联合使用多种震源类型可提升数据分辨率与振幅，进而改善成像潜力。不过成本、后勤保障与实施复杂度同样会对震源选型产生显著影响。