Magnitude calibrating functions for a multidimensional homogeneous system of reference stations |
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| Authors: | L Christoskov NV Kondorskaya J Van k |
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| Institution: | L. Christoskov, N.V. Kondorskaya,J. Vaněk |
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| Abstract: | Calibrating functions play a substantial role in the determination of earthquake magnitudes. Their shape and character is closely connected with the internal structure of the Earth, the distribution of velocities and attenuation of seismic waves in the Earth's body. These facts have been considered during the establishment of the Eurasian Homogeneous Magnitude System (EuHMS). The paper summarizes the procedures used for constructing the new complete set of calibrating functions for body and surface waves (vertical and horizontal components of P, S and L waves from medium period instruments, and vertical component of P waves from short period instruments).The calibrating functions were derived in the distance range between 20° and 100°, being based on several thousands of homogeneous observations for each wave type. The application of a HMS gives a possibility to derive the magnitude calibrating functions with a considerable degree of reliability due to the method of simultaneous optimization of the calibrating functions and the systems of station corrections. The magnitude calibrating functions for EuHMS represent the first complete set of calibrating functions, which are derived by the same standard method and initial observational material. A comparison with the existing calibrating functions shows that the application of σ and Q functions, presently used in the seismological practice for magnitude determinations, may lead to errors exceeding
of magnitude unit at certain epicentral distances, specific for each wave type. It appears that the internationally recommended Q functions are not admissible for magnitude determinations from short-period P waves. |
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