The 1994 Hokkaido Toho-oki earthquake sequence: the complex activity of intra-slab and plate-boundary earthquakes

2000 ◽  
Vol 121 (1-2) ◽  
pp. 39-58 ◽  
Author(s):  
Nobuyuki Morikawa ◽  
Tsutomu Sasatani
Keyword(s):  
Plate Boundary ◽  
Earthquake Sequence ◽  
Complex Activity

Tectonic Context and Possible Triggering of the 2019–2020 Puerto Rico Earthquake Sequence

2022 ◽  
Author(s):  
Marjolein Blasweiler ◽  
Matthew W. Herman ◽  
Fenna Houtsma ◽  
Rob Govers
Keyword(s):  
Puerto Rico ◽  
Fault Zone ◽  
Plate Boundary ◽  
Strike Slip ◽  
Global Navigation Satellite Systems ◽  
Earthquake Sequence ◽  
Motion Direction ◽  
Lateral Strike Slip ◽  
Coulomb Stress Changes ◽  
Stress Changes

Abstract An historically unprecedented seismic moment was released by crustal events of the 2019–2020 earthquake sequence near southwest Puerto Rico. The sequence involved at least two, and perhaps three interacting fault systems. The largest Mw 6.4 event was likely triggered by left lateral strike-slip events along the eastern extension of the North Boquerón Bay-Punta Montalva fault zone. The mainshock occurred in a normal fault zone that extends into a region where previous studies documented extensional deformation, beyond the Ponce fault and the Bajo Tasmanian fault. Coulomb stress changes by the mainshock may have triggered further normal-faulting aftershocks, left lateral strike-slip events in the region where these two fault zones interacted, and possibly right lateral strike-slip aftershocks along a third structure extending southward, the Guayanilla fault zone. Extension directions of the seismic sequence are consistently north-northwest–south-southeast-oriented, in agreement with the Global Navigation Satellite Systems-inferred motion direction of eastern Hispaniola relative to western Puerto Rico, and with crustal stress estimates for the overriding plate boundary zone.

Emergence of Low-Frequency Aftershocks of the 2019 Ridgecrest Earthquake Sequence

2022 ◽  
Author(s):  
Ayako Tsuchiyama ◽  
Taka’aki Taira ◽  
Junichi Nakajima ◽  
Roland Bürgmann
Keyword(s):  
Fluid Pressure ◽  
Plate Boundary ◽  
Low Frequency ◽  
Fault Zones ◽  
Aftershock Sequence ◽  
Earthquake Sequence ◽  
Near Surface ◽  
Hypocentral Distance ◽  
Generation Mechanisms ◽  
Stress Drops

ABSTRACT Low-frequency earthquakes (LFEs) generally have relatively stronger spectral components in the lower frequency range compared with what is expected for regular earthquakes based on their magnitude. LFEs generally occur in volcanic systems or deep (>∼15 km) in plate boundary fault zones; however, LFEs have also been observed in nonvolcanic, upper crustal settings. Because there are few studies that explore the spatiotemporal behaviors of LFEs in the shallow crust, it remains unclear whether the shallow-crustal LFEs reflect local attenuation in their immediate vicinity or differences in their source mechanism. Therefore, it is important to identify shallow-crustal LFEs and to characterize their spatiotemporal activity, which may also improve our understanding of LFEs. In this study, we focus on detecting shallow-crustal LFEs and explore the possible generation mechanisms. We analyze 29,646 aftershocks in the 2019 Ridgecrest, California, earthquake sequence, by measuring the frequency index (FI) to identify candidate low-frequency aftershocks (LFAs), while accounting for the magnitude dependency of the FI. Using small earthquakes (ML 1–3) recorded in the borehole stations to minimize the attenuation effects in near-surface layers, we identify 68 clear LFAs in total. Based on their distribution and comparisons with other seismic parameters measured by Trugman (2020), the LFAs possess distinct features from regular events in the same depths range, including low corner frequencies and low stress drops. Events in the close vicinity of LFAs exhibit lower average FI values than regular aftershocks, particularly if the hypocentral distance between an LFA and its neighbors is less than 1 km. Our results suggest that LFAs are related to local heterogeneity or a highly fractured fault zone correlated with an abundance of cross faults induced by the aftershock sequence at shallow depths. Zones of high pore-fluid pressure in intensely fractured fault zones could cause the bandlimited nature of LFAs and LFEs in general.

Effect of autumn feeding on dynamics of rectal congestion with excrement in carpathian breed honey bees

2020 ◽  
pp. 26-28
Author(s):  
Olesya V Strelbitskaya ◽  
◽  
Vladimir I. Kravchenko ◽  
Keyword(s):  
Point Of View ◽  
Theory And Practice ◽  
Complex Activity ◽  
Important Indicator ◽  
Apple Cider ◽  
Sugar Syrup ◽  
Main Indicator ◽  
Biological Laws ◽  
Honey Solution ◽  
Bee Colonies

Basic biological laws that govern the life of the bee family, as well as considering it as a whole organism, are necessary instruments for implementing effective methods of beekeeping and increasing the productivity of the industry. The study of the exterior features of bees must be carried out from different points of view for the concept of the complex activity of the bee family and in order to recommend methods for improving the preparation of bees for winter. Study of the mass of working bees and their rectum began to be used as the main indicator that affects the nature of the preparation of bee individuals for wintering. From the point of view of both theory and practice, filling the rectum with excrement in the autumn period will be an important indicator of an effective wintering in terms of preserving and further developing bee colonies. Effect of two kinds of liquid top feeding acidified with apple cider vinegar on the rectum congestion with excrement in working bees in the autumn, and the safety of bee colonies after winter was discussed in the article. The results of the indicators of the mass of working bees and intestinal mass when feeding two types of top dressing in the form of sugar syrup and honey solution with the addition of apple cider vinegar for the purpose of acidification are presented. The dynamics of rectal congestion in this group of bees is less compared to the group of bees receiving food in the form of sugar syrup. After wintering, during the spring audit, it was found that the safety of bees fed the autumn top dressing in the form of a honey solution with the addition of apple cider vinegar was 95% compared to bee families that received sugar syrup, the safety was 80.5%, with the detection of liquid excrement on the walls of hives and honeycombs

The interrelation of neurophysiological, psychological, and biochemical indicators in patients with occupational chronic mercury intoxication suffering from insomnia

2020 ◽  
Vol 60 (12) ◽  
pp. 904-910
Author(s):  
Elena V. Katamanova ◽  
Elena N. Korchuganova ◽  
Natalia V. Slivnitsyna ◽  
Irina V. Kudaeva ◽  
Oleg L. Lakhman
Keyword(s):  
Cerebral Cortex ◽  
Work Experience ◽  
Sleep Time ◽  
Serotonin Level ◽  
Complex Activity ◽  
Equivalent Dipole ◽  
Mercury Intoxication ◽  
Psychological Examination ◽  
Reticular System ◽  
Chronic Mercury Intoxication

Introduction. Despite the apparent connection of the existing neurological disorders and changes in the psycho-emotional sphere with sleep disorders in patients with chronic mercury intoxication (CRI), these relationships remain the least studied in the clinic neurointoxications. The study aimed to establish a connection between neurophysiological, biochemical, and psychopathological indicators in patients with occupational chronic mercury intoxication and insomnia. Materials and methods. Thirty-six patients took part in the examination in the remote period of CRI. The average age of patients in this group was 50.7±1.05 years, with an average work experience of 14.7±1.05. The authors carried out a psychological examination to determine the levels of depression, anxiety, asthenic state, computed electroencephalography (EEG), cognitive evoked potentials (CEP), polysomnography, the level of neurotransmitters. Results. The study showed that asthenization, when exposed to mercury, occurs due to a decrease in the limbic-hypothalamo-reticular complex activity (the presence of equivalent dipole sources of pathological activity in the area of diencephalic formations (thalamus, hypothalamus) in 56.2±5.6% of cases. The study showed a decrease in activity cerebral cortex, confirmed by weakening the coherent connections of the α-range in the occipital, central and frontal leads according to the data of coherent EEG analysis and changes on the part of the CEP. There was a direct correlation between the level of total sleep time and the serotonin level (rs=0.45), an inverse relationship between the level of depression and histamine level (rs=-0.56). Conclusion. The studies carried out to make it possible to establish the mechanisms of insomnia disorders in chronic mercury intoxication, which cause a weakening of the tone of the cerebral cortex and changes in neurotransmitter metabolism, as well as disorders of the reticular system with limbic structures. The study showed a close direct relationship between neurophysiological, psychological, and biochemical parameters in implementing insomnia in patients with chronic mercury intoxication.

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