FITTING AN ELLIPSE TO THE SET OF INTENSITY DATA POINTS OF VRANCEA EARTHQUAKES

Rashid Burtiev

doi:10.29081/jesr.v20i4.48

Abstract

<p>Fitting an ellipse to the set of intensity data points of earthquakes occurred on 11.10.1940, 07.04.1977, 31.08.1986, 30.05.1990 and 31.05.1990 is performed. Test criteria indicate that the ellipse smoothes the observed line of macroseismic field. For all earthquakes, focal axes of 5, 6 and 7 EMS-98 intensity zones are directed along the y-axis. For other zones are oriented along the parallels. This fact is one more acknowledgement of the anisotropy of a geophysical medium. Approximation of the set of points with an ellipse is performed using the method proposed by Fitzgibbon. </p>

Highlights

It is known that the intensity attenuation of seismic shakes with the distance determined geometrical disperse of the wave front, energy dissipation on inhomogeneities and absorption [1, 2]
Fitting an ellipse to the set of intensity data points of earthquakes occurred on 11.10.1940, 07.04.1977, 31.08.1986, 30.05.1990 and 31.05.1990 is performed
Test criteria indicate that the ellipse smoothes the observed line of macroseismic field

Summary

INTRODUCTION

It is known that the intensity attenuation of seismic shakes with the distance determined geometrical disperse of the wave front, energy dissipation on inhomogeneities and absorption [1, 2]. Attenuation equation assumes an isotropic medium and uniformity of distribution of seismic energy [4, 5]. In this case, the theoretical isoseists have a circular shape. In reality, from the epicenter of the earthquake isoseists disperse as ovals or curved form lines The shape of these isolines is influenced by factors: such as common - geometry of the source, velocity of detrusion waves, and regional – a material composition, a thickness of a soil stratum, level of ground waters, distinction of velocity in base breeds and in overlying stratum, physical properties of medium, type of soils, features of a geological structure of medium etc [6, 7]. The purpose of the given work is the study of the possibility to fit an ellipse to the set of intensity data points of Vrancea earthquakes

FITTING AN ELLIPSE TO A SET OF DATA POINTS OF MACROSEISMIC FIELD

THE GENERAL EQUATION OF AN ELLIPSE

CONCLUSIONS