Moment Tensor Solutions

Inhaltsverzeichnis

1. Frontmatter

2. ISOLA Code for Multiple-Point Source Modeling—Review

   Jiří Zahradník, Efthimios Sokos

   Abstract

   ISOLA software package has been developed to invert local or regional full-wave seismograms for single- and multiple-point source models. The code was introduced in 2003; since then it has been continually upgraded, and, presently, it can be considered a well-established tool, used worldwide. Originally, the code name came from ‘isolated asperities’, to be resolved at fault planes of large earthquakes. However, with time, the code has been adapted for very diverse applications, ranging from Mw 0.3 to Mw 9. Many research papers based on usage of ISOLA have been published (see References). Almost every new application is challenging—hence the code is continually updated. The objective of this work is to explain the basic principles of the method, review code status, demonstrate a few examples to attract new users, and shortly touch also future development. The code is free, and can be downloaded together with manual and test examples from http://seismo.geology.upatras.gr/isola/ (last accessed March 2018).

3. Seismic Moment Tensors in Anisotropic Media: A Review

   Václav Vavryčuk

   Abstract

   Seismic moment tensors of earthquakes in anisotropic media have more complicated properties than in isotropic media. For example. planar shear faulting produces pure double-couple mechanism in isotropy, but generally non-double-couple mechanism in anisotropy. The effects of anisotropy on moment tensors are numerically modelled and exemplified on acoustic emissions measured in the lab, on microearthquakes in the upper crust and on large deep-focus earthquakes in the Tonga subducting slab.

4. The Frequency-Domain Moment-Tensor Inversion: Retrieving the Complete Source Moment-Tensor Spectra and Time Histories

   Xiaoning Yang, Brian W. Stump, Mason D. Macphail

   Abstract

   When the wavelength of a seismic signal of interest is much longer than the dimension of the internal seismic source that generates the signal, whether it is an earthquake, an underground explosion or an underground mine collapse, the seismic source may be represented by a symmetric second-order moment tensor.

5. Berkeley Seismic Moment Tensor Method, Uncertainty Analysis, and Study of Non-double-couple Seismic Events

   Douglas S. Dreger

   Abstract

   For the past two decades, the Berkeley Seismological Laboratory has implemented and utilized as part of its routine operations a regional distance.

6. Estimating Stability and Resolution of Waveform Inversion Focal Mechanisms

   S. Scolaro, C. Totaro, D. Presti, Sebastiano D’Amico, G. Neri, B. Orecchio

   Abstract

   The main aim of this study is to describe several tools for testing the stability and resolution of waveform inversion focal mechanisms already successfully adopted for crustal earthquakes occurred in the Calabrian Arc region,

7. The Method of Cataclastic Analysis of Discontinuous Displacements

   Yu. L. Rebetsky, A. Yu. Polets

   Abstract

   Studying regularities of the spatial distribution and temporal variations of tectonic stress is one of the most important issues in a number of disciplines of the Earth sciences. In geodynamics, the problem of understanding of the stress state in the Earth’s crust and in the lithosphere is associated with the need to explain the mechanism of formation of the tectonic structures of various scale levels. In seismology, this is a problem of studying the formation mechanism of the earthquake source at the afterschock stage and the development of the post seismic relaxation at the aftershock stage. In geology, a stress state helps to establish interrelations of the formation conditions of the complex structures, discontinuous structures (slip faults) and other deformation structures with mineral deposits. In mining and oil production, stress data provide a safe and efficient exploration of natural resources.

8. Challenges in Regional Moment Tensor Resolution and Interpretation

   Simone Cesca, Sebastian Heimann

   Abstract

   The seismic moment tensor is a representation of a seismic source, described mathematically by a symmetric tensor of second order.

9. The Role of Moment Tensors in the Characterization of Hydraulic Stimulations

   Ismael Vera Rodriguez, James Rutledge, Sergey Stanchits

   Abstract

   Moment tensors are a useful tool to characterize different aspects about the mechanics of hydraulic stimulations.

10. Constrained Moment Tensors: Source Models and Case Studies

    Jan Šílený

    Abstract

    In recent decades, the earthquake mechanism, regardless of scale, has commonly come to be described by the moment tensor (MT).

11. Seismic Deformation Derived from Moment Tensor Summation: Application Along the Hellenic Trench

    Anastasia Kiratzi, Christoforos Benetatos, Filippos Vallianatos

    Abstract

    How continental areas deform has been a subject of intense research, especially in the prism of plate tectonics. The distribution of seismicity in continental areas is not confined to a single fault, but earthquakes are distributed over wide zones, hundreds or even thousands wide, which contain many faults. Within these deforming zones, as for example the Alpine-Himalayan Belt, there are blocks, which are relative aseismic, as the region of central Turkey, and are commonly referred to as microplates.

12. Estimation of Empirical Green’s Tensor Spatial Derivative Elements: A Preliminary Study Using Strong Motion Records in Southern Fukui Prefecture, Japan

    Michihiro Ohori

    Abstract

    The empirical Green’s tensor spatial derivative (EGTD) method, proposed by Plicka and Zahradnik (1998), has the potential to deal with differences in focal mechanisms between a targeted event and other small events, and to predict the ground motion for an event with an arbitrary focal mechanism.

13. Retrieval of the Seismic Moment Tensor from Joint Measurements of Translational and Rotational Ground Motions: Sparse Networks and Single Stations

    Stefanie Donner, Heiner Igel, Céline Hadziioannou, the Romy group

    Abstract

    Seismic moment tensors help us to increase our understanding about e.g. earthquake processes, tectonics, Earth or planetary structure. Based on ground motion measurements of seismic networks their determination is in general standard for all distance ranges, provided the velocity model of the target region is known well enough. For sparse networks in inaccessible terrain and planetary seismology, the waveform inversion for the moment tensor often fails. Rotational ground motions are on the verge of becoming routinely observable with the potential of providing additional constraints for seismic inverse problems. In this study, we test their benefit for the waveform inversion for seismic moment tensors under the condition of sparse networks. We compare the results of (1) inverting only traditional translational data with (2) inverting translational plus rotational data for the cases of only one, two, and three stations. Even for the single station case the inversion results can be improved when including rotational ground motions. However, from data of a single station only, the probability of determining the correct full seismic moment tensor is still low. When using data of two or three stations, the information gain due to rotational ground motions almost doubles. The probability of deriving the correct full moment tensor here is very high.

14. Overview of Moment Tensor Analysis in New Zealand

    John Ristau

    Abstract

    The determination of earthquake source parameters is of fundamental importance in seismological research. Moment tensor analysis involves fitting theoretical waveforms to observed broadband waveforms and inverting for the moment tensor elements, and allows for the calculation of focal mechanism (strike, dip, and rake), seismic moment (M₀), moment magnitude (M_w) which is calculated directly from M₀, and centroid depth of an earthquake. A comprehensive catalogue of moment tensor solutions is of great importance in seismic hazard analysis and tectonic studies. For example, seismic hazard estimates typically use M_w in earthquake forecasts and risk analysis, and moment release rates along plate boundaries are important in calculating predicted plate motions in tectonic studies.

15. Applications of Moment Tensor Solutions to the Assessment of Earthquake Hazard in Canada

    J. F. Cassidy, H. Kao, John Ristau, A. Bent

    Abstract

    Centroid Moment Tensor solutions (CMT’s) provide valuable information on the physics of an earthquake source, focal depth, and seismic moment. The earthquake rupture is described in terms of nine generalised force couples (a 3 × 3 matrix) that represent shear dislocation and volume change (see Jost and Herrmann 1989).

16. Intraplate Earthquakes in Europe—Source Parameters from Regional Moment Tensor Analysis

    Jochen Braunmiller

    Abstract

    Plate tectonics provides a highly successful framework to describe a wide range of geological observations invoking the motion of lithospheric plates. In its simplest form the plates are rigid and earthquakes are confined to boundaries where plates move relative to each other.

17. Source Characteristics of the January 8, 2013 (M w = 5.7) and May 24, 2014 (M w = 6.8) North Aegean Earthquakes Sequence

    Doğan Kalafat, Kıvanç Kekovalı, Ali Pınar

    Abstract

    The Aegean Sea, is one of the most seismically active areas of the Eastern Mediterranean region (Fig. 1). Generally, North Aegean Sea region has been tectonically developed after the collision of Arabian plate with the Eurasian in the Late Miocene time and the subsequent westward escape of the Anatolian Plate relative to the Eurasian Plate, during the Early Pliocene.

18. Investigating the Focal Mechanisms of the August 4th, 2003, 7.6, South Orkney Islands Earthquake and its Aftershocks Sequence

    M. P. Plasencia Linares, M. Guidarelli, M. Russi, G. F. Panza

    Abstract

    The \(M_w=7.6\) earthquake, known as Centenary Earthquake, occurred in the Scotia Sea region near the South Orkney Islands, Laurie Island, where is located the permanent Argentinean Antarctic Base Orcadas, here from 1997 operates a seismographic station ORCD, which has recorded several thousands of aftershocks, the most energetic ones recorded by all the instruments of the Antarctic Seismographic Argentinean-Italian Network (ASAIN). The aftershocks data available at ORCD station, till 60 days following the main shock were compiled. The plot of aftershocks rate with time was found to be oscillatory decay. Then, we inverted regional waveforms from ASAIN and International Federation of Digital Seismograph Networks (FSDN) stations to determine source parameters and source time functions for a set of aftershocks with magnitudes in the range 4.3–5.6 \(m_b\). For the regional inversion we applied a methodology for the determination of the seismic moment tensor by means of full waveform inversion. The results obtained reflect the normal character of the main system fault, characterizing the study area.