scholarly journals Assessment of glacial-earthquake source parameters

2017 ◽  
Vol 63 (241) ◽  
pp. 867-876 ◽  
Author(s):  
STEPHEN A. VEITCH ◽  
MEREDITH NETTLES
Keyword(s):  
Source Parameters ◽  
Seismic Source ◽  
Earthquake Source ◽  
Source Modeling ◽  
Front Position ◽  
Earthquake Source Parameters ◽  
Slow Earthquakes ◽  
Earthquake Force ◽  
Single Force ◽  
Remote Sensing Techniques

ABSTRACTGlacial earthquakes are slow earthquakes of magnitude M~5 associated with major calving events at near-grounded marine-terminating glaciers. These globally detectable earthquakes provide information on the grounding state of outlet glaciers and the timing of large calving events. Seismic source modeling of glacial earthquakes provides information on the size and orientation of forces associated with calving events. We compare force orientations estimated using a centroid-single-force technique with the calving-front orientations of the source glaciers at or near the time of earthquake occurrence. We consider earthquakes recorded at four glaciers in Greenland – Kangerdlugssuaq Glacier, Helheim Glacier, Kong Oscar Glacier, and Jakobshavn Isbræ – between 1999 and 2010. We find that the estimated earthquake force orientations accurately represent the orientation of the calving front at the time of the earthquake, and that seismogenic calving events are produced by a preferred section of the calving front, which may change with time. We also find that estimated earthquake locations vary in a manner consistent with changes in calving-front position, though with large scatter. We conclude that changes in glacial-earthquake source parameters reflect true changes in the geometry of the source glaciers, providing a means for identifying changes in glacier geometry and dynamics that complements traditional remote-sensing techniques.

scholarly journals Fully probabilistic seismic source inversion – Part 2: Modelling errors and station covariances

Solid Earth ◽  
2016 ◽  
Vol 7 (6) ◽  
pp. 1521-1536 ◽  
Author(s):  
Simon C. Stähler ◽  
Karin Sigloch
Keyword(s):  
Bayesian Inference ◽  
Cross Correlation ◽  
Likelihood Function ◽  
Body Wave ◽  
Source Parameters ◽  
Seismic Source ◽  
Earthquake Source ◽  
Source Inversion ◽  
Earthquake Source Parameters ◽  
Waveform Cross Correlation

Abstract. Seismic source inversion, a central task in seismology, is concerned with the estimation of earthquake source parameters and their uncertainties. Estimating uncertainties is particularly challenging because source inversion is a non-linear problem. In a companion paper, Stähler and Sigloch (2014) developed a method of fully Bayesian inference for source parameters, based on measurements of waveform cross-correlation between broadband, teleseismic body-wave observations and their modelled counterparts. This approach yields not only depth and moment tensor estimates but also source time functions. A prerequisite for Bayesian inference is the proper characterisation of the noise afflicting the measurements, a problem we address here. We show that, for realistic broadband body-wave seismograms, the systematic error due to an incomplete physical model affects waveform misfits more strongly than random, ambient background noise. In this situation, the waveform cross-correlation coefficient CC, or rather its decorrelation D = 1 − CC, performs more robustly as a misfit criterion than ℓp norms, more commonly used as sample-by-sample measures of misfit based on distances between individual time samples. From a set of over 900 user-supervised, deterministic earthquake source solutions treated as a quality-controlled reference, we derive the noise distribution on signal decorrelation D = 1 − CC of the broadband seismogram fits between observed and modelled waveforms. The noise on D is found to approximately follow a log-normal distribution, a fortunate fact that readily accommodates the formulation of an empirical likelihood function for D for our multivariate problem. The first and second moments of this multivariate distribution are shown to depend mostly on the signal-to-noise ratio (SNR) of the CC measurements and on the back-azimuthal distances of seismic stations. By identifying and quantifying this likelihood function, we make D and thus waveform cross-correlation measurements usable for fully probabilistic sampling strategies, in source inversion and related applications such as seismic tomography.

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.

Earthquake Source Parameters: Rapid Estimates for Tsunami Forecasts and Warnings

2021 ◽  
pp. 299-333
Author(s):  
Barry Hirshorn ◽  
Stuart Weinstein ◽  
Dailin Wang ◽  
Kanoa Koyanagi ◽  
Nathan Becker ◽  
...  
Keyword(s):  
Source Parameters ◽  
Earthquake Source ◽  
Earthquake Source Parameters

scholarly journals Tsunami hazard warning and risk prediction based on inaccurate earthquake source parameters

2016 ◽  
Vol 16 (2) ◽  
pp. 577-593 ◽  
Author(s):  
Katsuichiro Goda ◽  
Kamilla Abilova
Keyword(s):  
Risk Assessment ◽  
Early Stage ◽  
Source Parameters ◽  
Earthquake Source ◽  
Tsunami Early Warning ◽  
Earthquake Source Parameters ◽  
Tsunami Risk ◽  
Tsunami Warnings ◽  
Hazard Warning

Abstract. This study investigates the issues related to underestimation of the earthquake source parameters in the context of tsunami early warning and tsunami risk assessment. The magnitude of a very large event may be underestimated significantly during the early stage of the disaster, resulting in the issuance of incorrect tsunami warnings. Tsunamigenic events in the Tohoku region of Japan, where the 2011 tsunami occurred, are focused on as a case study to illustrate the significance of the problems. The effects of biases in the estimated earthquake magnitude on tsunami loss are investigated using a rigorous probabilistic tsunami loss calculation tool that can be applied to a range of earthquake magnitudes by accounting for uncertainties of earthquake source parameters (e.g., geometry, mean slip, and spatial slip distribution). The quantitative tsunami loss results provide valuable insights regarding the importance of deriving accurate seismic information as well as the potential biases of the anticipated tsunami consequences. Finally, the usefulness of rigorous tsunami risk assessment is discussed in defining critical hazard scenarios based on the potential consequences due to tsunami disasters.

Non-parametric spectral modelling of source parameters, path attenuation and site effects from broad-band waveforms of the Alborz earthquakes (2005–2017)

2019 ◽  
Vol 219 (3) ◽  
pp. 1514-1531
Author(s):  
Somayeh Ahmadzadeh ◽  
G Javan Doloei ◽  
Stefano Parolai ◽  
Adrien Oth
Keyword(s):  
Source Parameters ◽  
Broad Band ◽  
Site Amplification ◽  
Earthquake Source ◽  
Frequency Range ◽  
S Wave ◽  
Magnitude Range ◽  
Earthquake Source Parameters ◽  
Generalized Inversion Technique ◽  
Non Parametric

SUMMARY S-wave spectral amplitudes from 312 crustal earthquakes recorded at the Iranian National Broadband Seismic Network in the Alborz region between 2005 and 2017 are analysed in order to evaluate earthquake source parameters, path attenuation and site amplification functions using the non-parametric generalized inversion technique (GIT). We exploit a total number of 1117 seismograms with ML 3–5.6 in the frequency range 0.3–20 Hz. The evaluated non-parametric attenuation functions decay uniformly with distance for the entire frequency range and the estimated S-wave quality factor shows low Q values with relatively strong frequency dependence. We assume the omega-square source model to retrieve earthquake source parameters from the inverted source spectra. The obtained stress drops range from 0.02 to 16 MPa with a mean value of 1.1 MPa. Stress drop and radiated energy show fairly self-similar scaling with seismic moment over the available magnitude range; however, the magnitude range of this study is too narrow to draw a definite conclusion on source scaling characteristics. The obtained moment magnitude Mw and the local magnitude ML are linearly correlated and approximately equivalent in the range of Mw 3–4. For larger events, Mw generally underestimates ML by about 0.1–0.5 magnitude units. The estimated site amplification functions for horizontal component (GIT H) are nearly flat with no obvious pre-dominant frequency peaks for most stations, as expected for the sites of permanent broad-band seismic stations located on rock, though a few stations show amplification peaks from 1 to 8 Hz, with a maximum amplification of about a factor of 7 with respect to the reference site. The evaluated site responses for the vertical components present remarkable amplification or deamplification, leading to differences of the H/V amplitude levels in comparison with the GIT H amplification curves. The results of this study provide a valuable basis for predicting appropriate ground motions in a context of seismic hazard assessment.

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