The high-resolution community velocity model V2.0 of southwest China,constructed by joint body and surface wave tomography of data recorded at temporary dense arrays

The Sichuan-Yunnan area is located at the southeastern margin of the Tibetan Plateau,where tectonic movement is strong with deep and large faults distributed in a staggered manner,which results in strong seismic activities and severe earthquake hazards.Since the 21st century,several earthquakes of magnitude 7.0 or above occurred in this region,which have caused huge casualties and economic losses,especially the 2008 M_(s)8.0 Wenchuan earthquake.At present,earthquake monitoring and source parameter inversion,strong earthquake hazard analysis and disaster assessment are still the focus of seismological researches in the Sichuan-Yunnan region.Regional high-precision 3D community velocity models are fundamental for these studies.In this paper,by assembling seismic observations at permanent seismic stations and several temporary dense seismic arrays in this region,we obtained about 7.06 million body wave travel time data(including absolute and differential travel times)using a newly developed artificial intelligence body wave arrival time picking method and about 100,000 Rayleigh wave phase velocity dispersion data in the period range of 5-50 s from ambient noise cross-correlation technique.Based on this abundant dataset,we obtained the three-dimensional high resolution V_p and V_(s)model in the crust and uppermost mantle of southwest(SW)China by adopting the joint body and surface wave travel time tomography method considering the topography effect starting from the first version of community velocity model in SW China(SWChina CVM-1.0).Compared to SWChina CVM-1.0,this newly determined velocity model has higher resolution and better data fitness.It is accepted by the China Seismic Experimental Site as the second version of the community velocity model in SW China(SWChina CVM-2.0).The new model shows strong lateral heterogeneities in the shallow crust.Two disconnected low velocity zones are observed in the middle to lower crust,which is located in the Songpan-Ganzi block and the northern Chuandian block to the west of the Longmenshan-Lijiang-Xiaojinhe fault,and beneath the Xiaojiang fault zone,respectively.The inner zone of the Emeishan large igneous province(ELIP)exhibits a high velocity anomaly,which separates the two aforementioned low velocity anomalies.Low velocity anomaly is also shown beneath the Tengchong volcano.The velocity structures in the vicinity of the 2008 M_(s)8.0 Wenchuan earthquake,the 2013 M_(s)7.0Lushan earthquake and the 2017 M_(s)7.0 Jiuzhaigou earthquake mainly show high V_(p)and V_(s)anomalies and the mainshocks are basically located at the transition zone between the high and low velocity anomalies.Along with the segmentation characteristics of seismic activity,we suggest that areas with significant changes in velocity structures,especially in active fault zones,might have a greater potential to generate moderate to strong earthquakes.

Correlations of single photon emission computed tomography joints scan and bone metabolic markers in active rheumatoid arthritis

Objective To explore the correlation between quantitative value of joint bone scan by single photon emission computed tomography(SPECT)and serum bone metabolic markers in patients with active rheumatoid arthritis(RA).Methods Clinical data of 60 newly diagnosed RA patients were retrospectively collected in Department

Relationship between seismic structures and the diverse rupture processes of the 2023 Türkiye earthquake doublet

Recent geodetic and seismological observations of two major earthquakes in southeastern Türkiye in February 2023 have revealed complex rupture initiation,propagation,and segmentation along the East Anatolian Fault Zone(EAFZ)and surrounding regions.However,the role of upper crust structures along the EAFZ in determining the diverse rupture processes of this earthquake doublet remains unclear.To further investigate this,we employed double-difference location and seismic tomography techniques to determine high-resolution seismic velocities(V_(P),V_(S))and Poisson’s ratio(σ)structures using a multiparameter joint tomographic algorithm.Our dataset includes 100,833 high-quality source-receiver travel-time pairs of P-and Swaves.We find that the unique rupture processes of this earthquake doublet were primarily influenced by contrasting crustal seismic structures and localized geological settings.The M_(w)7.8 mainshock was initiated within a transitional edge zone characterized by a rigid part(asperity)of the seismogenic zone with sharp contrast variations in rock strength ranging from low to high along the EAFZ.In comparison,the M_(w)7.6 rupture originated in a ductile belt featuring fluid saturation with low-VP,low-VS,and high-σvalues that extended parallel to the Cardak Fault.The pronounced contrast structures observed along the former rupture can be attributed to the oblique collision system between the weakened section of the east Anatolian plateau and the brittle Arabian platform,while the latter rupture was initiated within the ductile structure associated with fluid intrusion caused by the northward subduction of the Cyprus slab and subsequent detachment.Furthermore,the occurrence of the first earthquake(E1)serves to alleviate shear stress on the second earthquake(E2)fault,potentially impeding the initiation of an E2 rupture.On the contrary,this event also significantly reduces the normal stress acting on the E2 fault due to a double left-lateral strike-slip system within a triangular region.This reduction not only results in a decrease of fault friction force and an increase in rock porosity but also induces lower strain drops and the redistribution of Coulomb stress,thereby contributing to the initiation of the E2 event.The proposed rupture pattern exceeds the conventional model that governs individual earthquake ruptures,offering new insights for mitigating potential seismic disasters in Türkiye.The lessons learned from this doublet event can contribute to reevaluating the ongoing risk of damaging earthquakes in China’s South-North Seismic Zone or other regions worldwide with comparable geological conditions.