Comparative Study On The Methods Of Earthquake Monitoring Capability Assessment

As a basic and important problem for assessment methods of actual work,scientific assessment for earthquake monitoring capability of China Seismic Network(CSN) is the key to further optimize the station-layout, improve the monitoring capability in the key areas, meet the demands of the earth science research and monitoring forecast. After half a century of development, earthquake monitoring capability and build of CSN have get fast development and even still in fast stage of development. Science research, monitoring forecast and "The national seismic intensity rapid reporting and early warning project" put forward higher requirements to scientific assessment of earthquake monitoring capability. This paper carries out the research according to the following problem: (1) How to assess existing earthquake monitoring capability of CSN scientifically? (2) What influenced and restricted the development of the earthquake monitoring capability of CSN, and how to achieve the top-notch monitoring capability promote requirements? (3) Multiple monitoring capability assessment methods give more options, in the practical work, how to choose scientific and effective monitoring capability assessment method?To solve these problems, this study investigated the seismic observation date of CNS with the national scale (70°?140°E, 5°?55°N, 1001stations) and north-south seismic belt (19°?45°E, 94°?110°N, 289 stations) during the period from 2008/10/01 to 2015/09/17. We used the "Probability-based magnitude of PMC method, EMR method and the "magnitude- maximum distance" method,and carried out introduction researches and comparison study. Besides, we developed a new assessment method for operation efficiency of seismic station. The recognition is as follows:Firstly, the PMC method have an advantage in objective assessment of actual output data from seismic network,independence of the relation of magnitude distribution, and the ability for assessment of weak active or non-seismic region. Based on the PMC method, we made an objective assessment on earthquake monitoring capability of China Seismic Network (CSN) after the completion of the "Tenth Five-Year Plan" project. The result indicated that the seismic monitoring capability was significantly higher in the north China and southeast coastal areas of China. By contrast,the minimum magnitude completeness in western especially in the southern of Qinghai-tibet plateau is ML4.5 and in offshore area is ML3.5. Needing to pay attention to the seismic monitoring capability was significantly weak, such as Qinghai-tibet plateau,frontier area and other regions.Secondly, in addition to mapping the seismic monitoring capability for entire CSN,we developed a new method named "seismic monitoring capability scale",and defined the seismic detection capability scale Dscore to analyze the statistical characters and spatial distribution of the seismic detection capabilities for each national and regional stations, which based on the amplitude contour curves. Additionally, the method of setting the "best objective function" of seismic detection capability was used to simulate the seismic monitoring capability improvement of CSN and "The national seismic intensity rapid reporting and early warning project" obtained by improving the conditions of observation. The result indicated that the Dscore scoring results of the 148 national stations are higher than the 853 regional stations systematically. The Dscore of western frontier regions (e.g. Xinjiang, Qinghai, Tibet, Inner Mongolia) and southeast offshore areas Fujian are higher than that of the eastern region with dense stations significantly. The simulation results showed that, on the basis of the existing station layout condition, through optimizing and improving the observation quality of seismic station, enhancing the operation and maintenance level, the monitoring capability of network and the detection capability of single station could be significantly enhanced in regions such as the western Inner Mongolia and the most areas of Guizhou. In addition, separately from the "bottom line" and the " best objective function" assessment "The national seismic intensity rapid reporting and early warning project" earthquake monitoring capability.Lastly, in order to explore the differences and causes of the assessing methods of monitoring capability of different seismic networks,this paper chooses the PMC,EMR and the "Magnitude - maximum distance" method at the north-south seismic belt region for comparative study. The problem of data quality consistency also considered which is not enough attention in previous studies, and the seismic events selected with at least three stations recorded. We find that the assessing results of three methods are significant difference, the difference between any two methods can reach to ML2.0 in some specific cases in the north-south seismic belt, and also have the statistical relationship MceEMR< Mp < Mr in general; the "Magnitude - maximum distance" method to get low value of Mr only related to the higher seismic station density region,The Mp results are significantly lower than other two methods in the north of 32°N, the mapping results of detection capability score results revealed that the station operational level and the complete degree in earthquake records analysis are the main reasons that the Mp results differ from other methods significantly,and data quality constraint criteria such as the number of recorded stations whether used or not,will cause significant difference on the result of the EMR method to other methods. Considering the seismic network actual situation in operation and the calculation principle in different assessment method, the PMC method is more reasonable and recommended for earthquake monitoring ability assessment work.In this paper, the results obtained will be of significance for scientific assessrment on earthquake monitoring capability, it can optimize the station-layout further and improve the monitoring capability in the border and sea areas in China, improve seismic network evaluation method and simulate the seismic monitoring capability improvement of "The national seismic intensity rapid reporting and early warning project".