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

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 is 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.

Characteristics of Sea Surface Current in the Bali Strait, Indonesia using HF Radar and Its Utilization in Safety Navigation

This paper was done by using the HF Radar data from 2018-2019 to study the characteristics of Sea Surface Current (SSC) in the Bali Strait. The data processing method was done by calculating the speed and SSC direction of the zonal and meridional components. Furthermore, SSC analysis was performed every hour and month by calculating the average of all data at the same hour and month. It was found that the unique SSC pattern in the Bali Strait occurred on the western side of Bali Island and the eastern side of Java Island. On the west side of the Bali Island, there was a decrease in SSC speed at 0.00-7.00 and 13.00-18.00, as well as a two-fold increase at 8.00-12.00 and 19.00-2.00, both of which were in a fluctuating speed range from 0-140 cm s-1 in the direction of dominant towards the south. On the eastern side of Java Island, SSC speed ranges from 0 to 40 cm s-1 all the time with the dominant direction heading from east to southeast. The monthly SSC pattern was also seen more clearly in this study, meanwhile during December-March the SSC rate was lower than during June-September, ranging from 0 to 20 cm s-1 and from 40 to 140 cm s-1, respectively. Furthermore, the two SSC patterns above can be simplified into two periods, namely periods of relaxation and agitation. This study also applies the device to ship accidents that occurred in the Bali Strait as case studies.

Tashkent gates

nformation about the first 12 gates located in the territory of Tashkent, its construction, as well as the names of these gates are stated. In the history of the ancient and ancient city of Tashkent you can find a lot of information about the city gates. Sources say that the castle was built in the IX-X centuries in the market area in the city center. It is surrounded by defensive walls. Gates are installed on the defensive walls. According to some sources, the number of ancient gates of Tashkent varied in different periods. For example, in the XVIII century there were 8 gates, and by the XIX century their number increased to 12. During this period, Tashkent was crossed by 8 main roads, which were the main trade routes. The city of Tashkent, a crossroads between East and West, sought to protect itself from external enemies. The defensive wall of the city had 12 gates (Takhtapul, Labzak, Kashgar, Kokand, Koymas, Beshyogoch, Kamalon, Samarkand, Kokcha, Chigatay, Sagbon, Karasaray) and two gates (i.e., a gate for 1 horseman). Of these, the gates of Labzak, Kashgar, Kokand, and Koymas were built on the eastern side of the part that was later annexed to the city, some of which were replaced. The names have also changed due to the relocation.

Climate on the Blanca Massif, Sangre de Cristo Mountains, Colorado, USA, during the Last Glacial Maximum

Temperature-index modeling is used to determine the magnitude of temperature depression on the Blanca Massif, Colorado, required to maintain steady-state mass balances of nine reconstructed glaciers at their extent during the Last Glacial Maximum (LGM). The mean temperature depression thus determined is ~8.6 +0.7/−0.9 °C where the uncertainties account for those inherent in the glacier reconstructions, in model parameters (e.g., melt factors), and possible modest changes in LGM precipitation. Associated equilibrium-line altitudes (ELAs) exhibit a statistically significant directional dependency being lower toward the north and east. Under the assumption that regional temperature change was uniform, required changes in precipitation vary systematically—also exhibiting a directional dependency coinciding with that in ELAs—and indicate increases (over modern) occurred on the eastern side of the massif while decreases occurred on the western side. This disparity represents a strengthening of a precipitation asymmetry, particularly winter precipitation, which exists today. The modern precipitation asymmetry may be a consequence of snow being blown over to the eastern side of the massif (advective transport) by southwesterly flow. Intensification of this flow during the LGM would have enhanced advection, and augmented snow accumulation on glaciers, thus explaining the lower ELAs and increased precipitation on that side of the massif.

DEM based morphotectonical analysis of the Kisgyőr Basin (Bükk Mts – Hungary)

The south-eastern part of the Bükk Mountains and the eastern side of its foothill, the Bükkalja are among the less explored regions of Hungary. Based on our examinations on the field, we found that the asymmetrical valley sections, the tipped escarpments and the formation of the Kisgyőr Basin cannot be explained by the differences in the rock quality. The asymmetrical shape of these landforms and the stream captures identified in the research area indicate significant structural geological changes. In our work, we proved the asymmetry in the topography by performing swath profile analysis, and we also examined the elevation data of the areas covered by the welded ignimbrites of the Tar Dacite Tuff Formation. The results confirmed our field observations. We found that, contrary to the results of previous research, the geological structural processes played a fundamental role in the formation of the Kisgyőr Basin and its surroundings.