A deep-learning-based approach for seismic surface-wave dispersion inversion(SfNet)with application to the Chinese mainland

Surface-wave tomography is an important and widely used method for imaging the crust and upper mantle velocity structure of the Earth.In this study,we proposed a deep learning(DL)method based on convolutional neural network(CNN),named SfNet,to derive the vS model from the Rayleigh wave phase and group velocity dispersion curves.Training a network model usually requires large amount of training datasets,which is labor-intensive and expensive to acquire.Here we relied on synthetics generated automatically from various spline-based vS models instead of directly using the existing vS models of an area to build the training dataset,which enhances the generalization of the DL method.In addition,we used a random sampling strategy of the dispersion periods in the training dataset,which alleviates the problem that the real data used must be sampled strictly according to the periods of training dataset.Tests using synthetic data demonstrate that the proposed method is much faster,and the results for the vS model are more accurate and robust than those of conventional methods.We applied our method to a dataset for the Chinese mainland and obtained a new reference velocity model of the Chinese continent(ChinaVs-DL1.0),which has smaller dispersion misfits than those from the traditional method.The high accuracy and efficiency of our DL approach makes it an important method for vS model inversions from large amounts of surface-wave dispersion data.

Crust and upper mantle structure of East Asia from ambient noise and earthquake surface wave tomography

The complex tectonic background of East Asia makes it an ideal region for investigating the evolution of the continental lithosphere,for which high-resolution lithospheric structural models are essential.In this study,we measured Rayleigh-wave phase-velocity dispersion curves at periods of 10-120 s and group velocity dispersion curves at periods of 10-140 s using event records from more than 1,000 seismic stations in and around China.By jointly inverting new and previously published dispersion data from ambient noise and earthquakes,we developed a high-resolution shear-wave velocity model down to a depth of~300 km beneath East Asia.Our model revealed heterogeneous lithospheric structures beneath East Asia,and allowed us to investigate the velocity structure of the entire lithosphere.We also derived crustal and lithospheric thickness models from the three-dimensional(3D)shear-wave model,revealing strong spatial heterogeneity and a general thinning trend of lithospheric thickness from west to east across the study region.Overall,our models reveal important lithospheric features beneath East Asia and provide a valuable baseline dataset for understanding continental-scale dynamics and evolution.

Evidence-Based Medicine Research on Prescriptions in Synopsis of the Golden Chamber in the Treatment of Pelvic Inflammatory Disease

Purpose: Based on the National Natural Science Foundation of China, we collect and sort out the literature published in approximately the last 30 years, which use prescriptions in Synopsis of the Golden Chamber to treat pelvic inflammatory disease (PID). This study provides theoretical basis for the treatment of PID;we recommend this achievement to colleagues. Method: Firstly, we searched and collected the literatures from last three decades in CNKI, Wanfang and VIP databases, which are about classical prescriptions treating endometriosis. Then, by screening all the literatures, we obtained the clinical research literatures and individual case reports. Finally, we went through the internal quality of the two categories of literatures to get the dominant prescriptions. Using a retrospective study of evidence-based medicine research, we comprehensively collect literature, standardize the disease spectrum, classify the evidence, and then evaluate the internal quality. Results: We refine 4 prescriptions which commonly are used in the treatment of PID;in other words, they are also the clinical symptoms of PID: Gui Zhi Fu Ling Wan symptom, which manifests blood stasis and cold-damp stagnancy;Dang Gui Shao Yao San symptom, which manifests disharmony of liver and spleen, qi-blood stasis and damp obstruction;Da Huang Mu Dan Tang symptom, which manifests the gathering toxic heat and qi-blood stasis;Yi Yi Fu Zi Bai Jiang San symptom, which manifests the internal toxic heat and qi-blood injury. Conclusion: This study is gospel for the patients with recurrent episodes of PID who can’t often use antibiotics. At the same time, it is also a green therapeutics which Chinese ancients dedicated to human medicine.

Fault Slip Model of 2013 Lushan Earthquake Retrieved Based on GPS Coseismic Displacements

Lushan Earthquake （-Mw 6.6） occurred in Sichuan Province of China on 20 April 2013, was the largest earthquake in Longmenshan fault belt since 2008 Wenchuan Earthquake. To better understand its rupture pattern, we focused on the influences of fault parameters on fault slips and performed fault slip inversion using Akaike＇s Bayesian Information Criterion （ABIC） method. Based on GPS coseismic data, our inverted results showed that the fault slip was mainly confined at depths. The maximum slip amplitude is about 0.7 m, and the scalar seismic moment is about 9.47x10TM N.m. Slip pattern reveals that the earthquake occurred on the thrust fault with large dip-slip and small strike-slip, such a simple fault slip represents no second sub-event occurred. The Coulomb stress changes （ACFF） matched the most aftershocks with negative anomalies. The in- verted results demonstrated that the source parameters have significant impacts on fault slip distri- bution, especially on the slip direction and maximum displacement.

Crustal Structure of Yunnan Province of China from Teleseismic Receiver Functions:Implications for Regional Crust Evolution

Yunnan Province is located on the southeastern margin of Tibet and represents an important marker in understanding the tectonic evolution of Tibetan Plateau. In this study, we calculated teleseismic P-wave receiver functions at 49 permanent broadband seismic stations in Yunnan Province and estimated crustal thickness and the bulk crust ratios of P-wave to S-wave velocities using the H-κ method together with more detailed crustal structural profiles from the common conversion point stacking method. There is a significant transition of Moho interface and lower crustal composition along latitude 26°N in northwestern Yunnan. Decrease of crustal thickness with a concomitant increase of Poisson’s ratio occurs at station CUX. An interesting phenomenon is that a step-like Moho fashion is observed at several stations, which might correspond to local thermal activities, such as partial melt/lower crust delamination. Our results show changes in crustal properties appear to be associated with varieties in upper mantle structure and compositions. We propose the controlling factor of the dynamic processes below 26°N is the result of eastern forward subduction of the Indian Plate; the northern part is controlled by the redirected material flow from the SE Tibet.

Distribution of Intra-Crustal Low Velocity Zones beneath Yunnan from Seismic Ambient Noise Tomography

Previous studies have reached consensus that low velocity zones are widespread in the crust beneath Yunnan region. However, the relationships between the low velocity zones and large faults, earthquake distribution are less investigated by available studies. By analyzing the seismic ambient noise recorded by Yunnan Seismic Networks and Tengchong volcano array, we construct a 3D crustal shear wave velocity model for the Yunnan region, which provides more details of the distribution of intra-crustal low velocity zones all over Yunnan. The distribution of low velocity zones shows different features at different depths. At shallow depths, the results are well correlated with near surface geological features. With increasing depth, the low velocity zones are gradually concentrated on the northern part of our study area, most likely reflecting variations in crustal thickness beneath the Yunnan region. The low velocity zones are truncated at depth by several large faults in Yunnan. It is interesting that most strong earthquakes（Ms≥5.0） occurred in Yunnan are distributed in low velocity zones or the transition zones between low and high velocity anomalies within the upper-to-middle crust. The crustal structure is composed of a brittle, seismically active upper-to-middle crust and a warm, aseismic lower crust.

Recovering Period of Postseismic Fluid Pressure in Fault Valve

The present study aims to reveal the recovering period of the postseismic fluid pressure in fault zone, offering an insight into earthquake recurrence. Numerical modeling is performed based on a 2D simple layered fault-valve model to simulate the fluid activities within the earthquake fault. In order to demonstrate the features of postseismic fluid pressure in natural state, the interference of tectonic movements is not considered. The recovering period of postseismic fluid pressure includes a sudden- changing period and a much longer fluctuating period. Modeling results show that fault permeability and porosity are sensitive parameters and reversely proportional to the recovering period of the fluid pressure in earthquake fault zone. When the permeability reduces from 10^-15 to 10^-18 m^2, the recovering period increases from 400 to 2 000 yrs, correspondently. The upper and lower fluid pressures are sepa- rated by the valve seal, causing their fluctuations in opposite tendencies.