Seismic instruments: article

Estimation of the efficiency of the new seismic network in Vietnam
V. Burmin1
T.L. Ngo2
T.T.H. Phung2
Q.K. Le2
1 Schmidt Institute of Physics of the Earth, Russian Academy of Sciences, Moscow, Russia
2 Institute of Geophysics of Vietnamese Academy of Science and technology, Hanoi, Vietnam
Journal: Seismic instruments
Tome: 53
Number: 3
Year: 2017
Pages: 74-86
UDK: 550.312
DOI: 10.21455/si2017.3-6
Keywords: seismic network, Vietnam, effectiveness of observing systems, magnitude, hypocenter
Аnnotation: The earthquakes that occur on the territory of Vietnam and especially in the East China Sea constitute a serious hazard for the population of Vietnam and its infrastructure in connection with the possible destruction and the tsunamis, which according to geological data occurred here in previous periods of time. That is why in the early 2000s, the government of Vietnam made a decision to modernize and expand the network of seismological observations on the territory of the republic. The modernization of the seismic network of Vietnam on the basis of wide-band seismic stations was initially planned in the amount of 20 stations, and then it was planned to increase the number of stations in this network to 30. In this connection, the problem of optimally locating these stations in the country for the purpose of forecasting earthquakes and studying the structure of the Earth‘ crust and upper mantle within the Vietnam territory. If you look at the map of Vietnam, it is easy to see that it is impossible to design a single optimal network of observations for localization of hypocenters of earthquakes throughout the country. The cause is the strong elongation of the territory from north to south. Any seismological network of observations for all such territory will be suboptimal. In this case, we can only talk about optimizing local observing networks for certain regions, such as the north, center and south of Vietnam. The article gives an estimation of efficiency (distribution of magnitude of completeness and errors in determining the coordinates of hypocenters of earthquakes) of a new network of seismological observations on the territory of Vietnam, consisting of 30 stations. To improve the quality of the network in central and southern parts of Vietnam, the authors of the article are proposing to place an additional six more seismic stations. Such a network will allow more accurate determination of the parameters of hypocenters in central and southern parts of Vietnam. When constructing an optimal network configuration, one of the main issues was choosing the effective radius of the network. The formula for determining the optimum radius of the network of seismic observations is obtained for the case of a uniform distribution of hypocenters in a certain region of cylindrical shape from the values of the radius of the base and the height of this cylinder. It follows from the formula given in the paper that the radius of the optimal network should not be less than the radius of the hypocentral region. In our case, the choice of network radius is limited by the state borders and the coastline of Vietnam. These limitations were taken into account in calculations to optimize the number of seismic stations and the configuration of their location in the country.