Прогноз возможно максимальных землетрясений в северо-западном районе Вьетнама

In this paper the authors presented some primary results of the application of Neural Network for Earthquake Magnitude Prediction in Tay Bac Viet Nam.Исследована возможность применения нейронных сетей для определения вероятности землетрясений в северо-западном районе Вьетнама

Gravity terrain correction for mainland territory of Vietnam

Terrain corrections for gravity data are a critical concern in rugged topography, because the magnitude of the corrections may be largely relative to the anomalies of interest. That is also important to determine the inner and outer radii beyond which the terrain effect can be neglected. Classical methods such as Lucaptrenco, Beriozkin and Prisivanco are indeed too slow with radius correction and are not extended while methods based on the Nagy’s and Kane’s are usually too approximate for the required accuracy. In order to achieve 0.1 mGal accuracy in terrain correction for mainland territory of Vietnam and reduce the computing time, the best inner and outer radii for terrain correction computation are 2 km and 70 km respectively. The results show that in nearly a half of the Vietnam territory, the terrain correction values ≥ 10 mGal, the corrections are smaller in the plain areas (less than 2 mGal) and higher in the mountainous region, in particular the correction reaches approximately 21 mGal in some locations of northern mountainous region. The complete Bouguer gravity map of mainland territory of Vietnam is reproduced based on the full terrain correction introduced in this paper

Some preliminary results of paleo-tsunami study in the coastal region of the Nghe An province, Vietnam

In the coastal region of the Nghe An province, the geomorphology is characterized by appearances of fields of arca granosa with placura placenta and hills of placura placenta with arca granosa, namely: The hills of placura placenta with the arca granosa shells in the Quynh Van and Nghi Tien communes; the fields of arca granosa with the placura placenta: deep-seated in the Quynh Nghia, Dien Chau and along the Nghi Yen coast  which have age of 4,500 - 4,300 yrs.; The appearance of the placura placenta-arca granosa shell’s fields and hills which do not originate from either marine transgression in the Holocene epoch, tectonic movement or artificiality; Our results suggest that there were three tsunami events occurring in the past during the periods of 4,500 - 4,300; 4,100 - 3,900 and 900 - 600 yrs., respectively in the region

NGHIÊN CỨU CẤU TRÚC SÂU KHU VỰC ĐỨT GÃY SÔNG SÀI GÒN BẰNG PHƯƠNG PHÁP TỪ TELUA

This paper presents the magnetotelluric sounding results  of  Cu  Chi  -  Ben  Cat profile across the  Saigon  River fault. Results obtained by one-dimensional inversion of the data of a typical station located near the middle of the profile show that the geoelectric structure of the study area consists of three layers, in which the resistivities of the superficial and the underlying layers are relatively low compared with that of the intermediate layer. This geoelectric structure is then used to estimate the influence of the equatorial electrojet on the magnetotelluric measurements carried out in the region. Magnetotelluric forward problems were calculated and compared for cases of the present and the absent of the equatorial electrojet model. Results show that in the range of periods less than 0.7s, the apparent resistivity measured are not affected by the equatorial electrojet. Therefore, the apparent resistivity data measured in the period range less than 0.7s of all stations on the profile have been used for two-dimensional inversion to obtain geoelectric cross-section acrossing the Saigon River fault. The geoelectric cross-section down to a depth of 10km obtained by two-dimensional inversion shows a geoelectric structure consist of 3 layers: a low resistivity superficial layer, a resistive intermediate layer, and a low resistivity underlying layer. The superficial layer is clearly related to the sedimentary series. The intermediate layer may relate to the intrusive and consolidated rocks. The underlying layer may reflect conductive materials causing by high-temperature condition at depth. The interface between the intermediate and the underlying layers at around 3km depth corresponds probably to the crystalline basement. The low resistivity regions under the C4 and C2 stations may be related to the Duong Minh Chau - Dau Tieng - Can Gio and the Saigon River faults, correspondingly.ReferencesS. C. Constable, R. L. Parker, and C. G. Constable, 1987. Occam’ s inversion: A practical algorithm for generating smooth models from EM sounding data, Geophysics, 52, 289-300. H. Grandis, M. Menvielle, and M. Roussignol, 1999. Bayesian inversion with Markovchains-I. Themagnetotelluric one-dimensional case, Geophys. J. Int., 138, 757-768. Trương Quang Hảo, Lương Văn Trương, 2005. Xác định một vài thông số của dòng điện xích đạo ở Việt Nam, Tuyển tập báo cáo Hội nghị khoa học kỹ thuật địa vật lý Việt Nam lần thứ 4, 47-70. Trương Quang Hảo, 1997. Thành tựu nghiên cứu Vật lý Địa cầu 1987-1997. Trung tâm Khoa học Tự nhiên và Công nghệ Quốc Gia, viện Vật lý Địa cầu, Nxb. KHKT, 202-236. Nguyễn Ngọc Hoa (chủ biên), 1995. Bản đồ địa chất và khoáng sản Việt Nam, tỷ lệ 1:200.000, tờ C-48-XI, Thành phố Hồ Chí Minh, Cục Địa chất và Khoáng sản Việt Nam, Hà Nội. Đặng Văn Hưng, 1987. Tính chất của trường điện từ tự nhiên miền xích đạo từ và độ chính xác của của phương pháp MTS ở Việt Nam, Tạp chí các Khoa học về Trái Đất, T.9, 2, 61-66. A. G. Jones, 1992. Electrical conductivity of the continental lower crust, Continental lower crust, Edi. D. M. Fountain, R. J. Arculus and R. W. Kay, 81-143. S. K. Lee et al, 2009. MT2DinvMatlab-A program in MATLAB and FORTRAN for two-dimensional magnetotelluric inversion, Computers Geosciences, 35, 1722-1734. Đỗ Văn Lĩnh (chủ biên), 2009. Báo cáo thuyết minh đề tài “Phân vùng nhỏ động đất khu vực thành phố Hồ Chí Minh”, Sở Khoa học và Công nghệ thành phố Hồ Chí Minh, 248tr. Lê Huy Minh, Nguyễn Văn Giảng, Nguyễn Trọng Vũ và Lại Cao Khiêm, 2004. Kết quả sơ bộ nghiên cứu cấu trúc sâu vùng đồng bằng Sông Cửu Long, Tuyển tập báo cáo Hội nghị Khoa học cơ bản, Thành phố Hồ Chí Minh 12/2004. Lê Huy Minh, Nguyễn Chiến Thắng, Lưu Việt Hùng, 2005. Kết quả đo sâu từ telua tuyến Chợ Gạo- Hóc Môn, Tuyển tập báo cáo Hội nghị Khoa học kỹ thuật Địa vật lý Việt Nam lần thứ 4, 149-161. Lê Huy Minh, Phạm Văn Ngọc, D. Boyer, Nguyễn Ngọc Thủy, Lê Trường Thanh, Ngô Văn Quân, G. Marquis, 2009. Nghiên cứu chi tiết cấu trúc đứt gãy Lai Châu - Điện Biên bằng phương pháp đo sâu từ tellur, Tạp chí Địa chất loạt A, 311, 11 -21. W. R. Peltier and J. F. Hermance, 1971. Magnetotelluric Fields of a Gaussian Electrojet, Canadian Journal of Earth Sciences, 8(3), 338-346. V. N. Pham, D. Boyer, T. K. T. Nguyen, and V. G. Nguyen, 1994. Deep ground-water investigation by combined VES/MTS methods near Ho Chi Minh City, Viet Nam, Ground water, 32, 4, 675-682. P. Tapponier et al., 1990. The Ailao Shan/Red River metamorphic belt: Tertiary left-lateral shear between Indochina and South China, Nature, 343, 431-437. Nguyễn Ngọc Thu, 2004. Xử lý tổng hợp tài liệu địa vật lý vùng thành phố Hồ Chí Minh, Luận án Tiến sĩ vật lý, Đại học Quốc Gia Tp. Hồ Chí Minh, 146tr. Cao Đình Triều, 2005. Trường địa vật lý và cấu trúc thạch quyển lãnh thổ Việt Nam. Nxb. KHKT, Hà Nội, 330tr. Cao Đình Triều, Phạm Huy Long, Đỗ Văn Lĩnh, Lê Văn Dũng, Cao Đình Trọng, 2013. Địa động lực hiện đại lãnh thổ Việt Nam. Nxb. Khoa học Tự nhiên và Công nghệ, 242tr.J. T. Weaver and A. K. Agarwal, 1993. Automatic 1-D inversion of magnetotelluric data by the method of modeling, Geophys. J. Int, 112, 115-123. This  paper  presents the magnetotelluric  sounding  results  of  Cu  Chi  -  Ben  Cat  profile  acrossing  the  Saigon  River fault. Results obtained by one-dimensional inversion of the data of a typical station located near the middle of the profile show that the geoelectric structure of the study area consists of three layers, in which the resistivities of the superficial and the underlying layers are relatively low compared with that of the intermediate layer. This geoelectric structure is then used to estimate the influence of the equatorial electrojet on the magnetotelluric measurements carried out in the region. Magnetotelluric forward problems were calculated and compared for cases of the present and the absent of the equatorial electrojet model. Results show that in the range of periods less than 0.7s, the apparent resistivity measured are not affected by the equatorial electrojet. Therefore, the apparent resistivity data measured in the period range less than 0.7s of all stations on the profile have been used for two-dimensional inversion to obtain geoelectric cross-section acrossing the Saigon River fault. The geoelectric cross-section down to a depth of 10km obtained by two-dimensional inversion shows a geoelectric structure consist of 3 layers: a low resistivity superficial layer, a resistive intermediate layer and a low resistivity underlying layer. The superficial layer is clearly related to the sedimentary series. The intermediate layer may relate to the intrusive and consolidated rocks. The underlying layer may reflect conductive materials causing by high temperature condition at depth. The interface between the intermediate and the underlying layers at around 3km depth corresponds probably to the crystalline basement. The low resistivity regions under the C4 and C2 stations may be related to the Duong Minh Chau - Dau Tieng - Can Gio and the Saigon River faults, correspondingly

Evaluation of awake prone positioning effectiveness in moderate to severe COVID-19

Evidence mainly from high income countries suggests that lying in the prone position may be beneficial in patients with COVID-19 even if they are not receiving invasive ventilation. Studies indicate that increased duration of prone position may be associated with improved outcomes, but achieving this requires additional staff time and resources. Our study aims to support prolonged (≥ 8hours/day) awake prone positioning in patients with moderate to severe COVID-19 disease in Vietnam. We use a specialist team to support prone positioning of patients and wearable devices to assist monitoring vital signs and prone position and an electronic data registry to capture routine clinical data

The global response: How cities and provinces around the globe tackled Covid-19 outbreaks in 2021

Background: Tackling the spread of COVID-19 remains a crucial part of ending the pandemic. Its highly contagious nature and constant evolution coupled with a relative lack of immunity make the virus difficult to control. For this, various strategies have been proposed and adopted including limiting contact, social isolation, vaccination, contact tracing, etc. However, given the heterogeneity in the enforcement of these strategies and constant fluctuations in the strictness levels of these strategies, it becomes challenging to assess the true impact of these strategies in controlling the spread of COVID-19.Methods: In the present study, we evaluated various transmission control measures that were imposed in 10 global urban cities and provinces in 2021 Bangkok, Gauteng, Ho Chi Minh City, Jakarta, London, Manila City, New Delhi, New York City, Singapore, and Tokyo.Findings: Based on our analysis, we herein propose the population-level Swiss cheese model for the failures and pit-falls in various strategies that each of these cities and provinces had. Furthermore, whilst all the evaluated cities and provinces took a different personalized approach to managing the pandemic, what remained common was dynamic enforcement and monitoring of breaches of each barrier of protection. The measures taken to reinforce the barriers were adjusted continuously based on the evolving epidemiological situation.Interpretation: How an individual city or province handled the pandemic profoundly affected and determined how the entire country handled the pandemic since the chain of transmission needs to be broken at the very grassroot level to achieve nationwide control

Fractal and Spectral Analysis of Seismicity in the Lai Chau Area (Vietnam)

The time dynamics of the instrumental seismicity recorded in the area of the Lai Chau reservoir (Vietnam) between 2015 and 2021 were analyzed in this study. The Gutenberg–Richter analysis of the frequency–magnitude distribution has revealed that the seismic catalog is complete for events with magnitudes larger or equal to 0.6. The fractal method of the Allan Factor applied to the series of the occurrence times suggests that the seismic series is characterized by time-clustering behavior with rather large degrees of clustering, as indicated by the value of the fractal exponent α≈0.55. The time-clustering of the time distribution of the earthquakes is also confirmed by a global coefficient of variation value of 1.9 for the interevent times. The application of the correlogram-based periodogram, which is a robust method used to estimate the power spectrum of short series, has revealed three main cycles with a significance level of p0.01 (of 10 months, 1 year, and 2 years) in the monthly variation of the mean water level of the reservoir, and two main periodicities with a significance level of p0.01 (at 6 months and 2 years) in the monthly number of earthquakes. By decomposing the monthly earthquake counts into intrinsic mode functions (IMFs) using the empirical decomposition method (EMD), we identified two IMFs characterized by cycles of 10 months and 2 years, significant at the 1% level, and one cycle of 1 year, significant at the 5% level. The cycles identified in these two IMFs are consistent with those detected in the water level, showing that, in a rigorously statistical manner, the seismic process occurring in the Lai Chau area might be triggered by the loading–unloading operational cycles of the reservoir

Ocena zagrożenia sejsmicznego dla kamieniołomów na rejonie Thuong Tan-Tan My (Wietnam)

This paper presents the seismic hazard assessment for Thuong Tan-Tan My quarries in Di An commune, Binh Duong province, Vietnam. Combination methods of gravity and magneto-telluric were used to estimate the dip angle and the width of the seismic source. The highest water column of 160 m will cause direct stress on the reservoir bottom with a maximum value of 1535.600 kPa and Coulomb stress of 68.693 kPa (at a depth of 2 km). The typical components of natural earthquake hazard (Mn.max = 5.0, depth of 10 km) in Thuong Tan - Tan My reservoir have the following values: peak ground acceleration PGA = 0.073 g ÷ 0.212 g; peak ground velocity PGV = 2.662 cm/s ÷ 7.984 cm/s; peak ground displacement PGD = 0.706 cm ÷ 1.918 cm at 10% probability of exceedance in 50 years. The typical components of triggered earthquake hazard (Mtr.max = 3.5, depth of 6 km) in Thuong Tan - Tan My reservoir have the following values: peak ground acceleration PGA = 0.024 g ÷ 0.172 g; peak ground velocity PGV = 0 ÷ 5.484 cm/s; peak ground displacement PGD = 0.061 cm ÷ 0.461 cm at 10% probability of exceedance in 50 years.W artykule przedstawiono ocenę zagrożenia sejsmicznego dla kamieniołomów na rejonie Thuong Tan-Tan My w gminie Di An w prowincji Binh Duong, Wietnamie. Do oszacowania kąta upadu i szerokości źródła sejsmicznego wykorzystano kombinację metod grawitacyjnych i magneto-tellurycznych. Najwyższy słup wody 160 m spowoduje bezpośrednie naprężenia na dnie zbiornika o maksymalnej wartości 1535,600 kPa i naprężeniu kulombowskim 68,693 kPa (na głębokości 2 km). Typowe składowe naturalnego zagrożenia trzęsieniem ziemi (Mn.max = 5,0, głębokość 10 km) w zbiorniku Thuong Tan-Tan My mają następujące wartości: szczytowe przyspieszenie gruntu PGA = 0,073 g ÷ 0,212 g; szczytowa prędkość gruntu PGV = 2,662 cm / s ÷ 7,984 cm / s; szczytowe przemieszczenie gruntu PGD = 0,706 cm ÷ 1,918 cm przy 10% prawdopodo-bieństwie przekroczenia za 50 lat. Typowe składowe wywołanego zagrożenia trzęsieniem ziemi (Mtr.max = 3,5, głębokość 6 km) w zbiorniku Thuong Tan-Tan My mają następujące wartości: szczytowe przyspieszenie ziemi PGA = 0,024 g ÷ 0,172 g; szczytowa prędkość gruntu PGV = 0 ÷ 5,484 cm / s; szczytowe przemieszczenie ziemi PGD = 0,061 cm ÷ 0,461 cm przy 10% prawdopodobieństwie za 50 lat

Metformin as adjunctive therapy for dengue in overweight and obese patients: a protocol for an open-label clinical trial (MeDO)

Background: Dengue is a disease of major global importance. While most symptomatic infections are mild, a small proportion of patients progress to severe disease with risk of hypovolaemic shock, organ dysfunction and death. In the absence of effective antiviral or disease modifying drugs, clinical management is solely reliant on supportive measures. Obesity is a growing problem among young people in Vietnam and is increasingly recognised as an important risk factor for severe dengue, likely due to alterations in host immune and inflammatory pathways. Metformin, a widely used anti-hyperglycaemic agent with excellent safety profile, has demonstrated potential as a dengue therapeutic in vitro and in a retrospective observational study of adult dengue patients with type 2 diabetes. This study aims to assess the safety and tolerability of metformin treatment in overweight and obese dengue patients, and investigate its effects on several clinical, immunological and virological markers of disease severity. Methods: This open label trial of 120 obese/overweight dengue patients will be performed in two phases, with a metformin dose escalation if no safety concerns arise in phase one. The primary endpoint is identification of clinical and laboratory adverse events. Sixty overweight and obese dengue patients aged 10-30 years will be enrolled at the Hospital for Tropical Diseases in Ho Chi Minh City, Vietnam. Participants will complete a 5-day course of metformin therapy and be compared to a non-treated group of 60 age-matched overweight and obese dengue patients. Discussion: Previously observed antiviral and immunomodulatory effects of metformin make it a promising dengue therapeutic candidate in appropriately selected patients. This study will assess the safety and tolerability of adjunctive metformin in the management of overweight and obese young dengue patients, as well as its effects on markers of viral replication, endothelial dysfunction and host immune responses. Trial registration: ClinicalTrials.gov: NCT04377451 (May 6th 2020)