Estimate of earthquake power dissipation from exhumed ancient faults (Gole Larghe fault zone, Italy).

2021 ◽  
Author(s):  
Francesco Lazari ◽  
Angela Castagna ◽  
Stefan Nielsen ◽  
Ashley W. Griffith ◽  
Phillip Resor ◽  
...  
Keyword(s):  
Temperature Gradient ◽  
Fault Zone ◽  
Power Dissipation ◽  
Temperature Increase ◽  
Source Parameters ◽  
Experimental Studies ◽  
Slip Zone ◽  
Melting Points ◽  
High Q ◽  
Earthquake Source Parameters

<p>Several earthquake source parameters cannot be estimated from the analysis of seismic waves, instead, they may be derived from field surveys and experimental studies. Among these parameters, the fault strength evolution (t<sub>f</sub> (t) in MPa) and the frictional power dissipation ( Q'= t<sub>f</sub> (t) V(t) in MW m<sup>-2</sup>, with V being the slip rate) during seismic slip control the moment release rate, the temperature increase in the slip zone and therefore the activation of coseismic fault dynamic weakening mechanisms. Frictional melts (preserved as pseudotachylytes) along the slip zone can be the result of relatively high Q'. In fact, shear heating is proportional to Q': the higher Q', the higher the heat production rate and, consequently, the faster the temperature increase in the slip zone and the steeper the temperature gradient in the boundary rocks (Nielsen et al., 2010). [PR1] The tonalite rocks used in this study come from the Gole Larghe Fault zone (Southern Alps, Italy), and they are made of minerals with different individual melting temperatures. The presence of a steep temperature gradient (high Q') with closely-spaced isotherms at the boundary walls, will cause the minerals to melt uniformly near the sliding surface (i.e. independently of their melting points), resulting in a relatively smooth pseudotachylyte-wall rock boundary. On the other hand, a gentle temperature gradient (low Q') with widely-spaced isotherms will mainly melt those minerals with low melting points, generating higher micro-roughness.</p><p>To consider these different scenarios, we collected samples of natural pseudotachylytes belonging to ‘wavy’ faults, together with samples of injection veins (tensile cracks with Q' ->  0). A ‘wavy’ fault presents shear cracks from compressional (high Q'), neutral, and extensional (low Q') domains along strike. We performed a series of experiments using a rotary shear apparatus (i.e., SHIVA, Di Toro et al., 2010) to produce artificial pseudotachylytes at increasing slip rates and normal stresses corresponding to values of increasing Q', ranging from 5 to 25 MW m<sup>-2</sup>. The micro-roughness is then measured from optical and scanning electron microscope images obtained both from natural and artificial samples for comparison. We found that in the experimental samples, the micro-roughness is inversely proportional to Q', as predicted by the theoretical model. Natural samples show similar trends with the higher micro-roughness present in the injection veins where  Q' ->  0. This study demonstrates the robustness of the relation between and fault micro-roughness in both natural and experimental samples. However, further investigations are required to calibrate this methodology to estimate quantitatively the frictional power dissipated during natural earthquakes.</p>

Earthquake source parameters at the sumatran fault zone: Identification of the activated fault plane

2010 ◽  
Vol 2 (4) ◽  
Author(s):  
Madlazim Kasmolan ◽  
Bagus Santosa ◽  
Jonathan Lees ◽  
Widya Utama
Keyword(s):  
Fault Zone ◽  
Moment Tensor ◽  
Source Parameters ◽  
Earthquake Source ◽  
Joint Analysis ◽  
Seismic Fault ◽  
Earthquake Source Parameters ◽  
Sumatran Fault ◽  
Centroid Position

AbstractFifteen earthquakes (Mw 4.1–6.4) occurring at ten major segments of the Sumatran Fault Zone (SFZ) were analyzed to identify their respective fault planes. The events were relocated in order to assess hypocenter uncertainty. Earthquake source parameters were determined from three-component local waveforms recorded by IRIS-DMC and GEOFON broadband lA networks. Epicentral distances of all stations were less than 10°. Moment tensor solutions of the events were calculated, along with simultaneous determination of centroid position. Joint analysis of hypocenter position, centroid position, and nodal planes produced clear outlines of the Sumatran fault planes. The preferable seismotectonic interpretation is that the events activated the SFZ at a depth of approximately 14–210 km, corresponding to the interplate Sumatran fault boundary. The identification of this seismic fault zone is significant to the investigation of seismic hazards in the region.

Seismic radiation from an SH line source in a laterally heterogeneous planar fault zone

1990 ◽  
Vol 80 (4) ◽  
pp. 971-994
Author(s):  
Yehuda Ben-Zion ◽  
Keiiti Aki
Keyword(s):  
Fault Zone ◽  
Line Source ◽  
Theoretical Calculations ◽  
Source Parameters ◽  
Homogeneous Medium ◽  
Vertical Layer ◽  
Material Heterogeneity ◽  
Homogeneous Half Space ◽  
Earthquake Source Parameters ◽  
Head Waves

Abstract A solution to the class of problems in which an SH line source is operating in a medium consisting of two quarter spaces with an arbitrary number of semi infinite vertical layers in between is given in a frequency-wavenumber domain. The general result is applied to a model with a single vertical layer, and synthetic seismograms are calculated for a source specified as an SH line dislocation at the interface between the vertical layer and the faster quarter space. The numerical examples demonstrate that moderate fault-normal material heterogeneity can have significant effects on the seismic response of a medium. The overall distribution of travel times, amplitudes, and motion polarities in the presence of fault zone material heterogeneity is different from a corresponding distribution in a homogeneous half space. The effects are most prominent near the fault zone, where head waves, surface waves, and trapped modes result in waveform complexities, large amplifications (over an order of magnitude in the fault zone itself), and first-motion polarities which are reversed from homogeneous medium predictions. The results imply that material heterogeneity should be included in fault zone models which are used for the interpretation of observed seismic data and theoretical calculations of near fault responses. Such models can be utilized to obtain important fault zone and earthquake source parameters.

Source Parameters for 1999 North Anatolian Fault Zone Aftershocks

2009 ◽  
Vol 166 (4) ◽  
pp. 547-566 ◽  
Author(s):  
Rengin Gök ◽  
Lawrence Hutchings ◽  
Kevin Mayeda ◽  
Doğan Kalafat
Keyword(s):  
Fault Zone ◽  
Source Parameters ◽  
North Anatolian Fault ◽  
North Anatolian Fault Zone

Strain to Ground Motion Conversion of DAS Data for Earthquake Magnitude and Stress Drop Determination

2021 ◽  
Author(s):  
Itzhak Lior ◽  
Anthony Sladen ◽  
Diego Mercerat ◽  
Jean-Paul Ampuero ◽  
Diane Rivet ◽  
...  
Keyword(s):  
Early Warning ◽  
Stress Drop ◽  
Source Parameters ◽  
Simulated Data ◽  
Earthquake Early Warning ◽  
Body Waves ◽  
Ocean Bottom ◽  
Correlated Noise ◽  
S Wave ◽  
Earthquake Source Parameters

<p>The use of Distributed Acoustic Sensing (DAS) presents unique advantages for earthquake monitoring compared with standard seismic networks: spatially dense measurements adapted for harsh environments and designed for remote operation. However, the ability to determine earthquake source parameters using DAS is yet to be fully established. In particular, resolving the magnitude and stress drop, is a fundamental objective for seismic monitoring and earthquake early warning. To apply existing methods for source parameter estimation to DAS signals, they must first be converted from strain to ground motions. This conversion can be achieved using the waves’ apparent phase velocity, which varies for different seismic phases ranging from fast body-waves to slow surface- and scattered-waves. To facilitate this conversion and improve its reliability, an algorithm for slowness determination is presented, based on the local slant-stack transform. This approach yields a unique slowness value at each time instance of a DAS time-series. The ability to convert strain-rate signals to ground accelerations is validated using simulated data and applied to several earthquakes recorded by dark fibers of three ocean-bottom telecommunication cables in the Mediterranean Sea. The conversion emphasizes fast body-waves compared to slow scattered-waves and ambient noise, and is robust even in the presence of correlated noise and varying wave propagation directions. Good agreement is found between source parameters determined using converted DAS waveforms and on-land seismometers for both P- and S-wave records. The demonstrated ability to resolve source parameters using P-waves on horizontal ocean-bottom fibers is key for the implementation of DAS based earthquake early warning, which will significantly improve hazard mitigation capabilities for offshore and tsunami earthquakes.</p>

Seismic doublets and a complex seismic sequence controlled by the rotation of the Juan Fernández microplate

2021 ◽  
Author(s):  
Simone Cesca ◽  
Carla Valenzuela Malebrán ◽  
José Ángel López-Comino ◽  
Timothy Davis ◽  
Carlos Tassara ◽  
...  
Keyword(s):  
Source Parameters ◽  
Strike Slip ◽  
Focal Mechanisms ◽  
Joint Analysis ◽  
Seismic Sequence ◽  
Local Data ◽  
Study Region ◽  
Coulomb Stress Changes ◽  
Earthquake Source Parameters ◽  
Stress Changes

<p> A complex seismic sequence took place in 2014 at the Juan Fernández microplate, a small microplate located between Pacific, Nazca and Antarctica plates. Despite the remoteness of the study region and the lack of local data, we were able to resolve earthquake source parameters and to reconstruct the complex seismic sequence, by using modern waveform-based seismological techniques. The sequence started with an exceptional Mw 7.1-6.7 thrust – strike slip earthquake doublet, the first subevent being the largest earthquake ever recorded in the region and one of the few rare thrust earthquakes in a region otherwise characterized by normal faulting and strike slip earthquakes. The joint analysis of seismicity and focal mechanisms suggest the activation of E-W and NE-SW faults or of an internal curved pseudofault, which is formed in response to the microplate rotation, with alternation of thrust and strike-slip earthquakes. Seismicity migrated Northward in its final phase, towards the microplate edge, where a second doublet with uneven focal mechanisms occurred. The sequence rupture kinematics is well explained by Coulomb stress changes imparted by the first subevent. Our analysis show that compressional stresses, which have been mapped at the northern boundary of the microplate, but never accompanied by large thrust earthquakes, can be accommodated by the rare occurrence of large, impulsive, shallow thrust earthquakes, with a considerable tsunamigenic potential.</p>

scholarly journals Earthquake source parameters that display the first digit phenomenon

2015 ◽  
Vol 22 (5) ◽  
pp. 625-632
Author(s):  
P. A. Toledo ◽  
S. R. Riquelme ◽  
J. A. Campos
Keyword(s):  
Seismic Moment ◽  
Waiting Times ◽  
Source Parameters ◽  
Tohoku Earthquake ◽  
Earthquake Source ◽  
Coseismic Slip ◽  
Self Organized ◽  
Earthquake Source Parameters ◽  
Self Organized Criticality

Abstract. We study the main parameters of earthquakes from the perspective of the first digit phenomenon: the nonuniform probability of the lower first digit different from 0 compared to the higher ones. We found that source parameters like coseismic slip distributions at the fault and coseismic inland displacements show first digit anomaly. We also found the tsunami runups measured after the earthquake to display the phenomenon. Other parameters found to obey first digit anomaly are related to the aftershocks: we show that seismic moment liberation and seismic waiting times also display an anomaly. We explain this finding by invoking a self-organized criticality framework. We demonstrate that critically organized automata show the first digit signature and we interpret this as a possible explanation of the behavior of the studied parameters of the Tohoku earthquake.

scholarly journals The use of parallel computing for the high-resolution determination of earthquake source parameters

2019 ◽  
pp. 68-75
Author(s):  
A. S. Fomochkina ◽  
V. G. Bukchin
Keyword(s):  
Parallel Computing ◽  
Focal Mechanism ◽  
Source Parameters ◽  
Nodal Plane ◽  
Earthquake Parameters ◽  
Earthquake Source Parameters ◽  
Detailed Search ◽  
High Degree ◽  
Special Case

Alongside the determination of the focal mechanism and source depth of an earthquake by direct examination of their probable values on a grid in the parameter space, also the resolution of these determinations can be estimated. However, this approach requires considerable time in the case of a detailed search. A special case of a shallow earthquake whose one nodal plane is subhorizontal is an example of the sources that require the use of a detailed grid. For studying these events based on the records of the long-period surface waves, the grids with high degree of detail in the angles of the focal mechanism are required. We discuss the application of the methods of parallel computing for speeding up the calculations of earthquake parameters and present the results of studying the strongest aftershock of the Tohoku, Japan, earthquake by this approach.

Determination of source parameters of small earthquakes from P-wave rise time

1973 ◽  
Vol 63 (2) ◽  
pp. 599-614 ◽  
Author(s):  
M. E. O'Neill ◽  
J. H. Healy
Keyword(s):  
Rise Time ◽  
Source Parameters ◽  
P Wave ◽  
Simple Method ◽  
Zero Crossing ◽  
Basic Measurement ◽  
Earthquake Source Parameters ◽  
Short Period ◽  
Stress Drops

abstract A simple method of estimating source dimensions and stress drops of small earthquakes is presented. The basic measurement is the time from the first break to the first zero crossing on short-period seismograms. Graphs relating these measurements to rise time as a function of Q and instrument response permit an estimate of earthquake source parameters without the calculation of spectra. Tests on data from Rangely, Colorado, and Hollister, California, indicate that the method gives reasonable results.

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