scholarly journals Rupture imaging of the 25 April 2015 MW7.9 Nepal earthquake from back-projection of teleseismic P waves

2018 ◽  
Vol 31 (4) ◽  
pp. 199-207
Author(s):  
Yong Qiu ◽  
◽  
Qiaoxia Liu
1988 ◽  
Vol 5 (1) ◽  
Author(s):  
M. R. Pandey ◽  
Peter Molnar

We have recompiled the descriptions of damage and destruction caused by the 15 January 1934 Bihar-Nepal earthquake, given by both Dunn et al. (1939) and by Major General Brahma Sumsher J. B. Rana (1935), to infer bounds on the dimensions of the rupture zone of that earthquake. The distribution of damage in northern India was very uneven, and much of that destruction was closely associated with slumping, fissuring, and tilting of the ground. The absence of any preferred orientation of the fissures and the prevalence of sand and water issued from fissures suggest that this disruption of  the  earth's  surface  was  limited  to  surficial  layers  and not to faulting of the  basement  beneath  that  area.  Thus  much  of  the  damage  in  northern India, perhaps the majority, was  not  due to  shaking  or  to  high  accelerations  of  the  ground, but rather to disruption ot the earth's surficial layers. Except for three short trips to parts of Nepal by.  J.  B.  Auden, Dunn and his colleagues has access to little information from Nepal, and their descriptions of the effects of the earthquake in Nepal were brief. Rana, however, made extensive compilations both of destroyed buildings and of casualties in various districts and towns in Nepal, and it appears that the greatest destruction lay in the parts of Nepal that Auden did not visit. Where Rana and Auden gave independent assessments of the damage, their reports agreed sufficiently well, that the particularly heavy toll reported to have been taken by the earthquake in the mountainous terrain of east-central Nepal probably is not an exaggeration.  This area, in fact, includes the epicenter of the earthquake recalculated from arrival times of P waves.


2009 ◽  
Vol 10 (4) ◽  
pp. n/a-n/a ◽  
Author(s):  
Yan Xu ◽  
Keith D. Koper ◽  
Oner Sufri ◽  
Lupei Zhu ◽  
Alexander R. Hutko

2020 ◽  
Author(s):  
Felipe Vera ◽  
Frederik Tilmann ◽  
Joachim Saul

<p><span>We present a back-projection method capable of being parameterized with multiples arrays. The rupture imaging is weighted to restrict uncertainties induced by non-symmetric azimuthal coverage of seismic arrays. The strategy also exploits the differences in time delays between </span><em><span>P</span></em><span> and depth phase (</span><em><span>pP)</span></em><span> waveforms by assuming them as proxies of the rupture that can be simultaneously back-projected. Surprisingly, this helps to improve the final results, even when depth phases overlap with the direct arrivals due to the rupture time exceeding the <em>pP-P</em> delay. Thus, the approach heightens the spatiotemporal resolvability enough to image rupture complexities. The rupture image of two large events demonstrates its robustness. The first one is the 14 November 2007 Mw 7.7 Tocopilla earthquake in northern Chile. The high-frequency rupture (0.5 - 2.0 Hz) encircles two asperities while the short-period energy radiated predominates up-dip of the coseismic slip. We propose the contribution of asperity rupture complexities and along-dip barriers to high-frequency emissions beyond the megathrust frictional structure. The second one is the Mw 7.5 Palu strike-slip earthquake, which occurred on 28 September 2018 in Sulawesi island. The back-projection reveals a prominent supershear rupture at a speed of 4.5 km/s. The result correlates with space geodesy data highlighting the successful recovery of fault structures. Finally, we discuss the potential and challenges of automating this analysis for near-real-time applications</span>, including near-source back-projection with strong-motion data.</p>


2010 ◽  
Vol 37 (3) ◽  
pp. n/a-n/a ◽  
Author(s):  
Sebastiano D'Amico ◽  
Keith D. Koper ◽  
Robert B. Herrmann ◽  
Aybige Akinci ◽  
Luca Malagnini
Keyword(s):  

Author(s):  
Yu Liu

The image obtained in a transmission electron microscope is the two-dimensional projection of a three-dimensional (3D) object. The 3D reconstruction of the object can be calculated from a series of projections by back-projection, but this algorithm assumes that the image is linearly related to a line integral of the object function. However, there are two kinds of contrast in electron microscopy, scattering and phase contrast, of which only the latter is linear with the optical density (OD) in the micrograph. Therefore the OD can be used as a measure of the projection only for thin specimens where phase contrast dominates the image. For thick specimens, where scattering contrast predominates, an exponential absorption law holds, and a logarithm of OD must be used. However, for large thicknesses, the simple exponential law might break down due to multiple and inelastic scattering.


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