It is well-known that Geosciences are strongly observation-dependent. The discoveries in Geosciences also strongly rely on the development of observation techniques. Whether earthquakes can be predicted or not has been debated in several decade years, due to limited instrument recorded data aiming at precursor extraction and earthquake cycle analysis, etc. in this situation it is very important to collect observation data for precursors in widely approaches. Since 1966 Xingtai earthquake occurred in China, the observation strategy of capturing earthquake precursor for the aim of prediction has been lasted more than 40 years. Even though the precursor is debated worldwide, a complex monitoring network has been built and improved step-by-step in station configuration as well as in techniques both in instrumentation and sampling frequency, a large amount of pre-seismic anomalies have been published in a series of cases in China by seismological Press in Beijing. Here we reviewed the observation progress in sampling frequency of groundwater and its effect on the understanding process of groundwater precursors from the early stage of continuous analog recording systems to the present stage of once per minute sampling frequency of digital techniques. Through comparing the anomaly process of once per minute sampling frequency data with 50Hz sampling frequency experiment observation data in Zhouzhi well before the 2008 Wenchuan earthquake, we declaimed that the presently designed once per minute sampling frequency digital observation techniques is not enough for capturing the earthquake precursors exactly. A systematically sampling frequency technique for future digital monitoring networks of groundwater level aiming at earthquake prediction is designed and proposed based on the above research.
This research is supported by National Natural Science Foundation projects with contract numbers of 41274061, 40674024 and 40374019.