No abstract

Earthquake early warning systems (EEWSs) are considered to be one of the most effective means for seismic risk mitigation, in terms of both losses and societal resilience, by releasing an alarm immediately after an earthquake occurs and before strong ground shaking arrives the target sites to be protected. To gain experience for the National System for Fast Seismic Intensity Report and Earthquake Early Warning project, we deployed a hybrid demonstration EEWS in the Sichuan–Yunnan border region with micro-electro-mechanical system-based sensors and broadband seismographs and low-latency data transmission. In this study, we described the structure of this EEWS and analyzed its performance in the first 2 yr from January 2017 to December 2018. During this test period, the EEWS detected and processed a total of 126 ML 3.0+ earthquakes, with excellent epicentral location and magnitude estimation. The average location and magnitude estimation errors for the first alert were 4.2±7.1  km and 0.2±0.31, respectively. For the earthquakes that occurred inside and outside the hybrid network, the first alert was generated 13.4±5.1  s and 26.3±13.5  s after the origin time (OT), respectively. We analyzed the performance of the EEWS for the 31 October 2018 M 5.1 earthquake, because it was the largest event that occurred inside the hybrid network during the test period. The first alert was obtained at 7.5 s after the OT, with a magnitude error of 0.1 magnitude unit, a location error of about 1 km, and a depth error of 8 km. Finally, we discussed the main differences between the EEWS’s estimates and the catalogs obtained by the China Earthquake Network Center, and proposed improvements to reduce the reporting time. This study demonstrated that we constructed a reliable, effective hybrid EEWS for the test region, which can provide sufficient support for the design of the National EEWS project.

We obtained the time-lapse cumulative slip before and after the 29 November 1999, Xiuyan, Liaoning, China, M_s = 5.4 earthquake by using "repeating events" defined by waveform cross-correlation. We used the seismic waveform data from the Liaoning Regional Seismograph Network from June 1999 to December 2006. Two "multiplets" located near the seismogenic fault of the 1999 Xiuyan earthquake and the 4 February 1975, Haicheng M_s = 7.3 earthquake, respectively, were investigated. For the "multiplet" that occurred before and after the 1999 Xiuyan earthquake, apparent pre-shock accelerating-like slip behavior, clear immediate-post-seismic change, and relaxation-like post-seismic change can be observed. As a comparison, for the "multiplet" near the 1975 Haicheng earthquake which occurred a quarter century ago, the cumulative slip appears linear with a much smaller slip rate

SUMMARYWe calculated noise correlation function (NCF) around the Longmenshan fault zone which is responsible for the Wenchuan M S 8.0 earthquake on May 12, 2008. We used 58 station pairs in the investigation. The time period considered was from April 21, 12:00 a.m. local time, to May 12, 2008, 12:00 a.m. local time, 22 days before the occurrence of the earthquake. Correlation coefficient between NCF of each day and its previous day (the 'second cross-correlation') was calculated. Four hundred second long waveform is used in the 'second cross-correlation'. Before the earthquake, there seemed to be an apparent variation of such correlation coefficient, and such a pattern seemed coherent for almost all the station pairs. From the scattering around the periodical variations of the 'second cross-correlation', a seemingly precursory change can be observed. However, at the present stage, it is still hard to draw any conclusion about the precursory changes before the earthquake.

Objective. We aimed to evaluate the advantages of preoperative digital design of skin flaps to repair fingertip defects during the COVID-19 pandemic. We combined digital design with a 3D-printed model of the affected finger for preoperative communication with fingertip defect patients under observation in a buffer ward. Methods. From December 2019 to January 2021, we obtained data from 25 cases of 30 fingertip defects in 15 males and 10 females, aged 20-65 years old (mean 35 ± 5 years). All cases were treated by digitally designing preoperative fingertip defect flaps combined with a 3D-printed model. Preoperative 3D Systems Sense scanning was routinely performed, 3-matic 12.0 was used to measure the fingertip defect area ranging from 1.5   cm × 3.5   cm to 2.0   cm × 5.0   cm , and the skin flap was designed. The flap area was 1.6   cm × 3.6   cm to 2.1   cm × 5.1   cm . CURA 15.02.1 was used to set parameters, and the 3D model of the affected finger was printed prior to the operation. Full-thickness skin grafts were taken from donor areas for repair. Results. No vascular crises occurred in any of the 25 cases, and all flaps survived. The postoperative follow-up occurred over 3-12 months. All patients were evaluated 3 months after operation according to the trial standard of hand function evaluation of the Chinese Hand Surgery Society. The results showed that 20 cases had excellent outcomes (80%), four cases had good outcomes (16%), and one case had a fair outcome (4%). The excellent and good rate was 96%. Conclusions. During the COVID-19 epidemic, fingertip defects were treated with preoperative digital design of fingertip defect flaps combined with 3D printing. Precision design saves surgery time and improves the success rate of surgery and the survival rates of skin flaps. In addition, 3D model simulations improve preoperative communication efficiency, and the personalized design improves patient satisfaction.