超动态变形场长时间观测系统

A SUPER-DYNAMIC DEFORMATION MEASUREMENT SYSTEM WITH LONG-TIME PARALLEL CONTINUOUS ACQUISITION

地震模拟实验通过稳态加载获得失稳滑动或破裂事件来模拟地震过程。实验中,稳态变形与失稳滑动交替出现。由于无法事先确定失稳发生的时刻与持续时间,且一次实验中有可能产生多次失稳事件,为了保证在极其短暂的失稳瞬间获得足够的数据以分析震源力学过程,数据采集系统需要从实验开始直至结束一直保持高速连续工作。一般的实验进程可能会持续十几h,因此需要巨大的存储空间。尽管还没有确切地了解失稳信号的频率上限,但以往的实验已经证明信号的频率会达到几百甚至几千Hz,所以采样频率应当达到MHz量级以上。在这种连续长时间获取高频数据的情况下,还要保持较高的信噪比。此外,以往的实验已经证明,震源力学场具有复杂的空间结构,难以用少数几个测点来描述,需要对几十个以上的测点进行同步观测。长时间连续记录、高分辨率高频采样与多点同步观测4项技术手段的联合使用对观测系统的技术指标提出了巨大的挑战。为此,文中研发了一套高信噪比的64通道、16位分辨率、4MHz并行采集频率、可以连续记录几十h的超动态变形场观测系统。利用这套系统可以实现应变、声发射及位移等多种信号的同步采集,便于分析各种物理量之间的转换关系。

In the simulation experiments of earthquakes in laboratory,the instability slip or rupture events are obtained through steady state loading to simulate earthquake processes. In the experiments,steady-state deformation and unstable sliding occur alternately. It is hard to determine the origin time and duration of the instability event of fault,and there may be many instability events in one experiment. Therefore,in order to ensure that sufficient data is obtained at the extremely short instability moment to analyze the mechanical process of the earthquake source,the data acquisition system is required to continuously collect data at high-speed from the beginning of the experiment until the end,and the lasting time can be more than ten hours,so it requires huge storage space. Although the upper frequency limit of the instability signal is unknown exactly,but the previous experiments have shown that the frequency of the signal will reach hundred to several kilohertz,so the sampling frequency of the data acquisition should be above megahertz. In this case of long-time continuous high-frequency data acquisition, it is still necessary to maintain a high signal-to-noise ratio.Furthermore,previous studies have proved that the source mechanics field has a complex spatial structure,which is difficult to describe with a few measuring points,and it is necessary to perform simultaneous measurements of the source mechanics field for dozens or more measuring points. The combination of long-term continuous recording,high-resolution high-frequency sampling and multipoint simultaneous measurement poses a huge challenge to the technical indicators of the observing system. With the method for composing distributed synchronous acquisition machine group by using multiple high-resolution high-frequency sampling computers, a super dynamic deformation measurement system of high signal-to-noise ratio,which features 64-channel,16-bit resolution,4 MHz sampling frequency,and parallel continuous acquisition with tens of hours was developed. This system can realize the synchronous acquisition of various signals,such as strain,acoustic emission,electromagnetic waves and displacement,so it is convenient for analyzing the conversion relationship between various physical quantities.