Spatio-temporal distribution of shallow very-low-frequency earthquakes between December 2020 and January 2021 in Kumano-nada, Nankai subduction zone, detected by a permanent seafloor seismic network

We estimate the hypocenter locations and the centroid moment tensor solutions of the shallow very-low-frequency earthquake (sVLFE) activity that occurred in the Kumano-nada region of the Nankai Trough megathrust zone in central Japan from December 2020 to January 2021. Using seafloor observation data, we examined the detailed spatio-temporal distribution of the sVLFE activity. During this episode, the activity area was within the vicinity in which the sVLFE activity has been observed in the past and can be divided into two major parts. The sVLFE activity started from the eastern side and remained there for the first 5 days and then migrated to the western side via secondary expansion. The eastern active area is located just below the outer ridge and coincides with the location where the paleo-Zenith Ridge subducted. The western activity area is centered between the outer wedge and the outer ridge with the primary active area being at the outer wedge. Comparing the activity in the eastern and western areas, the eastern side is more active, but the individual moment releases on this side are smaller than those on the western side. This may indicate a difference in the fluid pressure along the plate boundary between the eastern and western areas. After the second expansion of the active area, we observed several migration patterns within the expanded area with a faster velocity than those of the initial and second expansions. The direction of these migrations is opposite to that of the first and second expansions. This indicates that the fluid pressure and/or stress level in the sVLFE generation region changed with time within this episode. Furthermore, many waveforms with sVLFE characteristics were observed at only one or a few observation points near the trough axis in the middle to latter half of January 2021. This indicates the occurrence of small-scale sVLFEs in the vicinity of the trough axis at the end of this sVLFE episode. Graphical Abstract

A Pragmatic Analysis of Illocutionary Act in a Selected Presidential Speech on COVID-19

This paper aims at studying the illocutionary speech acts: direct and indirect to show the most dominant ones in a presidential speech delivered by the USA president. The speech is about the most critical health issue in the world, COVID-19 outbreak. A descriptive qualitative study was conducted by observing the first speech delivered by president Trump concerning coronavirus outbreak and surveying the illocutionary acts: directive, declarative, commissive, expressive, and representative. Searle's (1985) classification of illocutionary speech acts is adopted in the analysis. What are the main types of the illocutionary speech acts performed by Trump in his speech?; Why does Trump perform illocutionary acts?; and What is the purpose behind using the most dominant acts? The study is of significant value as it displays how the USA's leader addresses his people linguistically using the illocutionary acts. It helps to understand how language is used to deal with certain actions and how it affects the hearers’ viewpoints. The study concludes that two types of illocutionary acts show a significant frequency of occurrence: representatives and declarative. Such result appears due to the purpose behind the discourse under analysis. The other three types of illocutionary acts are of very low frequency. The purpose of the speech and the identity of the figure who delivers it significantly influence the choice of the illocutionary acts. Since the figure who delivers the speech is the president, he has the authority to declare the issue, give instructions concerning the actions that will be taken in the light of this issue and clarify the situation.

Application of Very Low Frequency (VLF) Method for Estimating Karst Underground River in Tanjungsari District

Drought is the main problem for clean water needs in Tanjungsari district. This research aims to provide information on the existence of underground river for deep well drilling. The methods used are geologic-structural analysis and application of Very Low Frequency (VLF) methods. Strike and dip measurements of 150 joints were conducted in the research area. Analysis using rosette diagram shows that the main geologic-structure orientation has a direction of Northwest - Southeast and Northeast – Southwest. Very Low Frequency (VLF) acquisition was measured across the possible occurrence of subsurface water flow directions predicted from geologic-structural analysis. The length of the VLF acquisition line is 2500 meters with 30 m spacing and 108 points acquisitions. The direction of VLF line is N 2700 E. The result shows that there are 2 locations that have high conductivity values, appearing at 1800 meters and 2200 meters. The results of this structural and VLF analyses indicate the existence of underground river at the location of 454326 N, 9105870 E.

The state of response of autonomic nervous system in children with mitral valve prolapse

The article presents summarized materials on connective tissue dysplasia of the heart, primary mitral valve prolapse, dysfunction of the autonomic system. Aim of research: to estimate the condition of autonomic nervous system in children with primary mitral valve prolapse. We examined 106 children with mitral valve prolapse aged from 13 to 17 years old on the clinical base of city hospital “Center of mother and child” in Vinnitsya. Research included time and frequency domain (evaluation with cardiointervalography. Final results were compared with the control group records. The results showed no statistical significance among time domain parameters in the main group of children. All these indices displayed tendency to sympathetic and parasympathetic autonomic nervous system tonus increase in boys. However, sympathicotonia tendency was noted in girls only. Frequency domain parameters showed similar results, compared with the previous. Nevertheless, very low frequency parameters had statistically significant difference in both subgroups of patience with mitral valve prolapse, including males (3205.8±190.9 against 1717±154, р<0.05) and females (3280±220.1 against 1433±811, р<0.05). There were no statistically significant difference among other frequency domain parameters. Conclusions: we estimated that children with mitral valve prolapse have imbalanced autonomic homeostasis manifested by tone disturbances of both autonomic vegetative system branches with sympathetic predominance. Patients with primary mitral valve prolapse generally have increased sympathetic tone - both boys and girls - according to spectral analysis of heart rate variability indices, heart rate oscillation power of a very low frequency in particular (p<0.05). In children with mitral valve prolapse, the tone of parasympathetic nervous system is generally normal; there is a tendency to its increase in boys and decrease in girls. These children should be under close medical supervision by pediatricians and cardiologists.

Outbreak of Negative Narrow Bipolar Events in Two Mid-Latitude Thunderstorms Featuring Overshooting Tops

Lightning discharges are the electrical production in thunderclouds. They radiate the bulk of radio signals in the very low-frequency and low-frequency (VLF/LF) that can be detected by ground-based receivers. One kind of special intra-cloud lightning discharges known as narrow bipolar events (NBEs) have been shown to be rare but closely linked to the convective activity that leads to hazardous weather. However, there is still lack of understanding on the meteorological conditions for thunderstorm-producing NBEs, especially for those of negative polarity, due to their rare occurrence. In this work, we aim to investigate what meteorological and electrical conditions of thunderclouds favor the production of negative NBEs. Combining with the VLF/LF radio signal measured by Jianghuai Area Sferic Array (JASA), S-band Doppler radar observation and balloon sounding data, two mid-latitude thunderstorms with outbreaks of negative NBEs at midnight in East China were analyzed. The comparison with the vertical radar profile shows that the bursts of negative NBEs occurred near thunderclouds with overshooting tops higher than 18 km. Manifestation of negative NBEs is observed with a relatively low spectrum width near thundercloud tops. Our findings suggest that the detection of negative NBEs would provide a unique electrical means to remotely probe overshooting tops with implications for the exchange of troposphere and stratosphere.

Studi Hidrogeofisika Gunung Malabar Sebagai Gunung Tertinggi pada Sistem Hidrologi Cekungan Bandung

Gunung Malabar merupakan gunung tertinggi pada gugus pegunungan yang mengitari Cekungan Bandung Purba. Kawasan ini tersusun oleh berbagai pegunungan kecil, yaitu Gunung Haruman, Gunung Puntang dan dataran tinggi Pangalengan. Vegetasi di kawasan Gunung Malabar masih cukup lebat dan kawasan ini juga sering mengalami hujan dengan intensitas yang tinggi. Kondisi tersebut menjadikan Gunung Malabar sebagai recharge area dan catchment area yang ideal dengan area cukup luas. Artikel ini mengulas hasil penelitian hidrologi menggunakan metode geofisika untuk mengkaji pengaruh kawasan Gunung Malabar terhadap sistem hidrologi Cekungan Bandung Purba. Metode yang digunakan pada penelitian ini adalah Resistivitas-DC dan Very Low Frequency. Selain itu, pengukuran sifat fisik dan kimia air juga dilakukan untuk mendapatkan nilai kualitas baku mutu air permukaan berdasarkan parameter TDS, pH, dan EC. Pengukuran Resistivitas-DC dilakukan di dua wilayah yaitu di Lereng Utara Gunung Malabar, diperoleh rentang nilai resistivitas air tanah sekitar (1.4-70)Ωm, sedangkan di lereng barat Gunung Malabar, diperoleh rentang nilai resistivitas air tanah sekitar (20-150)Ωm. Kombinasi metode Resistivitas-DC dengan VLF di lereng barat Gunung Malabar menunjukkan bahwa recharge area dari sistem hidrologi di Gunung Malabar terbentuk pada zona lapisan dangkal (sekitar 15 m) dan menengah (sampai dengan 40 m). Selain itu, studi ini juga menunjukkan kualitas air tanah di kawasan Gunung Malabar. Hasil yang diperoleh dari pengukuran sifat fisik dan kimia air yaitu diperoleh rentang untuk parameter TDS dengan nilai (20-70) ppm, pH dengan rentang 6.20-8.48, dan EC dalam rentang (43-130)KataKunci : Cekungan Bandung, Gunung Malabar, Resistivitas-DC, Very Low Frequency, sifat fisik dan kimia air.

Mild poikilocapnic hypoxia increases very low frequency haemoglobin oxygenation oscillations in prefrontal cortex

Background The aim of the study was to investigate the effect of mild cerebral hypoxia on haemoglobin oxygenation (HbO2), cerebrospinal fluid dynamics and cardiovascular physiology. To achieve this goal, four signals were recorded simultaneously: blood pressure, heart rate / electrocardiogram, HbO2 from right hemisphere and changes of subarachnoid space (SAS) width from left hemisphere. Signals were registered from 30 healthy, young participants (2 females and 28 males, body mass index = 24.5 ± 2.3 kg/m2, age 30.8 ± 13.4 years). Results We analysed the recorded signals using wavelet transform and phase coherence. We demonstrated for the first time that in healthy subjects exposed to mild poikilokapnic hypoxia there were increases in very low frequency HbO2 oscillations (< 0.052 Hz) in prefrontal cortex. Additionally, SAS fluctuation diminished in the whole frequency range which could be explained by brain oedema. Conclusions Consequently the study provides insight into mechanisms governing brain response to a mild hypoxic challenge. Our study supports the notion that HbO2 and SAS width monitoring might be beneficial for patients with acute lung disease.