Comparison of the Recorded Significant Duration of the Lushan Earthquake with Empirical Model Predictions

2019 ◽  
Vol 109 (6) ◽  
pp. 2325-2339
Author(s):  
Yuzhu Bai

Abstract Using 72 free‐field accelerograms with the closest site‐rupture distances (Rrup) less than 300 km, this study calculates the recorded significant duration of the 2013 Mw 6.7 Lushan earthquake and compares the calculated results with empirical model predictions. The significant duration parameters are for 5%–75% (D5–75) and 5%–95% (D5–95) of the normalized Arias intensity. For Rrup<150  km, the models of Du and Wang (2017; hereafter, DW17) are relatively less biased in predicting the Lushan significant duration. The goodness‐of‐fit results indicate that the models of DW17, Afshari and Stewart (2016; hereafter, AS16), and Kempton and Stewart (2006; hereafter, KS06) are the best models to predict D5–75 of the Lushan event. Meanwhile, most of the selected empirical models predict the Lushan event better for D5–75 than for D5–95. Moreover, the enrichment of high‐frequency components of ground motion causes the recorded D5–95 of the Lushan event to be larger than median predictions in high‐frequency bands. Among the five selected earthquakes (1994 Mw 6.7 Northridge, 2003 Mw 6.5 San Simeon, 2004 Mw 6.6 Niigata, 2008 Mw 7.9 Wenchuan, and 2013 Mw 6.7 Lushan earthquakes), the Lushan earthquake is predicted relatively better by all empirical models. The intraevent and interevent residuals of AS16 model from China earthquakes are within the scatter of those from the events in the Next Generation Attenuation‐West2 (NGA‐West2) database, indicating that the China earthquake significant duration is consistent with the model developed through the NGA‐West2 database. Furthermore, the regional dependences of significant duration are not observed for the Wenchuan or the Lushan earthquake.

Author(s):  
G. Y. Fan ◽  
J. M. Cowley

It is well known that the structure information on the specimen is not always faithfully transferred through the electron microscope. Firstly, the spatial frequency spectrum is modulated by the transfer function (TF) at the focal plane. Secondly, the spectrum suffers high frequency cut-off by the aperture (or effectively damping terms such as chromatic aberration). While these do not have essential effect on imaging crystal periodicity as long as the low order Bragg spots are inside the aperture, although the contrast may be reversed, they may change the appearance of images of amorphous materials completely. Because the spectrum of amorphous materials is continuous, modulation of it emphasizes some components while weakening others. Especially the cut-off of high frequency components, which contribute to amorphous image just as strongly as low frequency components can have a fundamental effect. This can be illustrated through computer simulation. Imaging of a whitenoise object with an electron microscope without TF limitation gives Fig. 1a, which is obtained by Fourier transformation of a constant amplitude combined with random phases generated by computer.


2019 ◽  
Vol 14 (7) ◽  
pp. 658-666
Author(s):  
Kai-jian Xia ◽  
Jian-qiang Wang ◽  
Jian Cai

Background: Lung cancer is one of the common malignant tumors. The successful diagnosis of lung cancer depends on the accuracy of the image obtained from medical imaging modalities. Objective: The fusion of CT and PET is combining the complimentary and redundant information both images and can increase the ease of perception. Since the existing fusion method sare not perfect enough, and the fusion effect remains to be improved, the paper proposes a novel method called adaptive PET/CT fusion for lung cancer in Piella framework. Methods: This algorithm firstly adopted the DTCWT to decompose the PET and CT images into different components, respectively. In accordance with the characteristics of low-frequency and high-frequency components and the features of PET and CT image, 5 membership functions are used as a combination method so as to determine the fusion weight for low-frequency components. In order to fuse different high-frequency components, we select the energy difference of decomposition coefficients as the match measure, and the local energy as the activity measure; in addition, the decision factor is also determined for the high-frequency components. Results: The proposed method is compared with some of the pixel-level spatial domain image fusion algorithms. The experimental results show that our proposed algorithm is feasible and effective. Conclusion: Our proposed algorithm can better retain and protrude the lesions edge information and the texture information of lesions in the image fusion.


Author(s):  
Priya R. Kamath ◽  
Kedarnath Senapati ◽  
P. Jidesh

Speckles are inherent to SAR. They hide and undermine several relevant information contained in the SAR images. In this paper, a despeckling algorithm using the shrinkage of two-dimensional discrete orthonormal S-transform (2D-DOST) coefficients in the transform domain along with shock filter is proposed. Also, an attempt has been made as a post-processing step to preserve the edges and other details while removing the speckle. The proposed strategy involves decomposing the SAR image into low and high-frequency components and processing them separately. A shock filter is used to smooth out the small variations in low-frequency components, and the high-frequency components are treated with a shrinkage of 2D-DOST coefficients. The edges, for enhancement, are detected using a ratio-based edge detection algorithm. The proposed method is tested, verified, and compared with some well-known models on C-band and X-band SAR images. A detailed experimental analysis is illustrated.


2021 ◽  
pp. 35-44
Author(s):  
Ю.Г. Матвиенко ◽  
И.Е. Васильев ◽  
Д.В. Чернов ◽  
В.И. Иванов ◽  
С.В. Елизаров

The accuracy of the location of acoustic emission (AE) sources in the concentrator zones (central holes 5 mm in diameter) located at a distance of 40 mm from the receiving transducers during tensile tests of steel, aluminum alloy and composite flat specimens with dimensions of 550x50x4 mm was evaluated. Calculated speed dependence of propagation of pulses on the level of their amplitude and the partial energy of the high-frequency components of the spectrum is studied. With the threshold method of signal registration, the error in the location of AE event sources arising in the near zone of the receiving transducers at a distance 𝛥L<0.1 m can significantly exceed 10% relative to the base size (B) of the location area, when B<0.5 m. Moreover, with a decrease in the distance 𝛥L<0.05 m, the level of possible error will increase, reaching 20-30% relative to the basic size of the antenna array, when recording pulses with an amplitude level um<60 dB and a fraction of the energy of high-frequency spectrum components not exceeding 10%.


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