On geometric complexity of earthquake focal zone and fault system: A statistical study

TL;DR

This paper reviews methods for analyzing the geometric complexity of earthquake sources, focusing on focal mechanisms and the role of CLVD components, using global earthquake data to explore their significance.

Contribution

It introduces a detailed analysis of earthquake source complexity through quaternion representation and examines the presence of CLVD components in global seismic data.

Findings

Fault barriers lack CLVD components

CLVD component likely zero in tectonic earthquakes

More data needed for definitive conclusions

Abstract

We discuss various methods used to investigate the geometric complexity of earthquakes and earthquake faults, based both on a point-source representation and the study of interrelations between earthquake focal mechanisms. We briefly review the seismic moment tensor formalism and discuss in some detail the representation of double-couple (DC) earthquake sources by normalized quaternions. Non-DC earthquake sources like the CLVD focal mechanism are also considered. We obtain the characterization of the earthquake complex source caused by summation of disoriented DC sources. We show that commonly defined geometrical fault barriers correspond to the sources without any CLVD component. We analyze the CMT global earthquake catalog to examine whether the focal mechanism distribution suggests that the CLVD component is likely to be zero in tectonic earthquakes. Although some indications support this conjecture, we need more extensive and significantly more accurate data to answer this question fully.