Methods for the IMS Regional Kinematic Calibration
Abstract
Among the problems related to CTBT a very important role belongs to the calibration of the regional travel times (regional kinematic calibration). The success in solving this task would significantly improve the accuracy of the weak seismic event location by the system. The methods that are applied to perform this kind of calibration are assumed in the present paper. All these methods can be broken into two principal groups: methods for direct calibration and those utilizing the velocity model of the media that is to be developed in an intermediate stage. Direct methods are used to construct the time correction surfaces making use of previously learned seismological experience (regional travel time tables) or directly employing the experimental data. The first approach represents the try to perform the task through the linear combination of regional travel time tables (godographs) and their errors. Another technique is a kind of spatial interpolation of the regional observations for given station. Indirect methods solve the calibration problem in two steps. Initially the 3-D velocity model of the media is being produced by the inversion of the observations. Afterwards the field of travel times is generated on the base of the velocity model. Methods inside the group differ depending upon what way is chosen for the reverse kinematic problem solution. Currently the velocity models are being built by "try-and-drop" technique or by tomographic inversion. The tomographic P-models developed till now do not possess the horizontal resolution enough to be successfully applied in a regional scale. The main reason of poor lateral resolution for the uppermost mantle comes from low amount and uneven distribution of regional P-wave observations used to produce the global tomographic models. The reliability of 3-D model constructed by "try-and-drop" method is unknown but its using is still reasonable unless enough data for the area to be calibrated have been collected.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 2000
- Accession Number
- ADA529973
Entities
People
- Nikolai A. Vasiliev