Spatial distribution of the difference between the magnitudes of the main shock and the largest aftershock in the circum-Pacific belt

1990 ◽  
Vol 80 (5) ◽  
pp. 1180-1189
Author(s):  
Theodoros M. Tsapanos
Keyword(s):  
Spatial Distribution ◽  
Main Shock ◽  
Plate Boundaries ◽  
Plate Interface ◽  
The Difference ◽  
Back Arc ◽  
Earthquake Sequences ◽  
Largest Aftershock ◽  
Magnitude Difference ◽  
Good Number

Abstract The distribution of the magnitude difference D1 between the main shock and the largest aftershock for large circum-Pacific earthquakes is observed to be peaked at 1.2 magnitude units, in accord with Bath's law, but also at 1.8 magnitude units. The peak at 1.8 has been not noted before and is shown here with the T-test to be statistically valid. The observed spatial distribution of the sequences is the basis to suggest that, along circum-Pacific convergent plate boundaries, values of D1, tend to be larger for earthquake sequences within back-arc areas as compared to sequences closer to the plate interface, although admittedly a good number of exceptions to this generalization are also observed to exist.

Common features of the reservoir-associated seismic activities

1972 ◽  
Vol 62 (2) ◽  
pp. 481-492 ◽  
Author(s):  
Harsh K. Gupta ◽  
B. K. Rastogi ◽  
Hari Narain
Keyword(s):  
Main Shock ◽  
Detailed Examination ◽  
Factors Affecting ◽  
B Values ◽  
Common Features ◽  
Rate Of Increase ◽  
Tremor Frequency ◽  
Earthquake Sequences ◽  
Largest Aftershock ◽  
Frequency Magnitude

abstract A detailed examination of the behavior of earthquakes associated with over a dozen artificial lakes shows that, in all cases, the tremors were initiated or their frequency increased considerably following the lake filling and that their epicenters were mostly located within a distance of 25 km from the lakes. Among the factors affecting the tremor frequency are the rate of increase of water level, duration of loading, maximum levels reached, and the period for which the high levels are retained. The study of these reservoir-associated earthquake sequences reveals that the ratio of the largest aftershock to the main shock is high (about 0.9), and the b values are also high in the frequency-magnitude relation, which is contrary to the normal earthquakes of the concerned regions.

Stress drop and aftershocks

1973 ◽  
Vol 63 (4) ◽  
pp. 1433-1446
Author(s):  
S. J. Gibowicz
Keyword(s):  
Stress Drop ◽  
Main Shock ◽  
Local Magnitude ◽  
Principal Characteristics ◽  
Fault Surface ◽  
A Value ◽  
High Magnitude ◽  
Aftershock Sequences ◽  
The Difference ◽  
Largest Aftershock

abstract Eighteen aftershock sequences, nine from California and nine from New Zealand, are studied. It is found that a general relationship exists between the local magnitude ML and the stress drop in the main shock. The stress drop in the main earthquake determines the principal characteristics of the aftershock sequences. A low stress drop leads to a low value of the coefficient b, high magnitude of the largest aftershock, and short duration, and conversely. A sequence is arbitrarily considered to be over when the rate of aftershock occurrence falls to a value of one shock per day. The duration depends on the area of fault surface and the stress drop in the main shock. For an average stress drop, the coefficient b has a value of 0.8 to 0.9, and the difference in magnitude between the main shock and the largest aftershock is 1.2, a relation often called Båth's law.

Variation of the frequency-magnitude relation during earthquake sequences in New Zealand

1973 ◽  
Vol 63 (2) ◽  
pp. 517-528 ◽  
Author(s):  
S. J. Gibowicz
Keyword(s):  
New Zealand ◽  
Main Shock ◽  
Earthquake Swarm ◽  
Rock Deformation ◽  
Laboratory Studies ◽  
Aftershock Sequences ◽  
Stress Changes ◽  
Earthquake Sequences ◽  
Largest Aftershock ◽  
Frequency Magnitude

abstract Seven New Zealand earthquake sequences are studied statistically. These comprise six aftershock sequences and one earthquake swarm. The magnitude-stability law of Lomnitz does not hold. During the aftershock sequences the coefficient b, governing the frequency-magnitude relationship, is found to increase rapidly after the main shock, and then to decrease until the occurrence of the largest aftershock, when it again begins to increase. During the earthquake swarm, the coefficient b decreases logarithmically with time. This can be explained in terms of stress changes and is consistent with laboratory studies on rock deformation.

A study of the aftershocks and focal mechanism of the Salinas-Watsonville earthquakes of August 31 and September 14, 1963

1965 ◽  
Vol 55 (1) ◽  
pp. 85-106 ◽  
Author(s):  
Agustin Udias
Keyword(s):  
Focal Mechanism ◽  
Seismic Activity ◽  
Main Shock ◽  
San Andreas Fault ◽  
San Andreas ◽  
Principal Axes ◽  
Mobile Stations ◽  
Earthquake Sequences ◽  
Background Seismic Activity

Abstract The earthquake sequences connected with the earthquakes of August 31 and September 14, 1963 in the Salinas-Watsonville region of California are here studied with reference to the background seismic activity. A very favorable distribution of permanent and mobile stations in this area permits the analysis to include earthquakes of small magnitudes. The mechanism of the larger aftershocks of both sequences is found to be similar to the mechanism of the main shock of September 14, 1963. The orientation of the principal axes of stress derived from the focal mechanism of the September 14 earthquake, is related to the strike of the San Andreas fault.

Observations of the Coyote Lake, California earthquake sequence of August 6, 1979

1980 ◽  
Vol 70 (2) ◽  
pp. 559-570 ◽  
Author(s):  
R. A. Uhrhammer
Keyword(s):  
San Francisco ◽  
Fault Zone ◽  
Strong Earthquake ◽  
Main Shock ◽  
B Value ◽  
Aftershock Sequence ◽  
The South ◽  
The North ◽  
Temporal And Spatial Characteristics ◽  
Largest Aftershock

abstract At 1705 UTC on August 6, 1979, a strong earthquake (ML = 5.9) occurred along the Calaveras fault zone south of Coyote Lake about 110 km southeast of San Francisco. This strong earthquake had an aftershock sequence of 31 events (2.4 ≦ ML ≦ 4.4) during August 1979. No foreshocks (ML ≧ 1.5) were observed in the 3 months prior to the main shock. The local magnitude (ML = 5.9) and the seismic moment (Mo = 6 × 1024 dyne-cm from the SH pulse) for the main shock were determined from the 100 × torsion and 3-component ultra-long period seismographs located at Berkeley. Local magnitudes are determined for the aftershocks from the maximum trace amplitudes on the Wood-Anderson torsion seismograms recorded at Berkeley (Δ ≊ 110 km). Temporal and spatial characteristics of the aftershock sequence are presented and discussed. Some key observations are: (1) the first six aftershocks (ML ≧ 2.4) proceed along the fault zone progressively to the south of the main shock; (2) all of the aftershocks (ML ≧ 2.4) to the south of the largest aftershock (ML = 4.4) have a different focal mechanism than the aftershocks to the north; (3) no aftershocks (ML ≧ 2.4) were observed significantly to the north of the main shock for the first 5 days of the sequence; and (4) the b-value (0.70 ± 0.17) for the aftershock sequence is not significantly different from the average b-value (0.88 ± 0.08) calculated for the Calaveras fault zone from 16 yr of data.

scholarly journals Top-down estimation of carbon monoxide emissions from the Mexico Megacity based on FTIR measurements from ground and space

2012 ◽  
Vol 12 (11) ◽  
pp. 29915-29965 ◽  
Author(s):  
W. Stremme ◽  
M. Grutter ◽  
C. Rivera ◽  
A. Bezanilla ◽  
A. R. Garcia ◽  
...  
Keyword(s):  
Carbon Monoxide ◽  
Spatial Distribution ◽  
Mexico City ◽  
Emission Flux ◽  
Top Down ◽  
Solar Absorption ◽  
Surface Emission ◽  
The Difference ◽  
Anthropogenic Pollutant ◽  
Total Column

Abstract. Continuous carbon monoxide (CO) total column densities above the UNAM campus in Mexico City have been derived from solar absorption infrared spectroscopic measurements since October 2007. Its diurnal evolution is used in the present study in conjunction with other ground-based and satellite data to develop a top-down emission estimate of the annual CO emission of the Mexico City Metropolitan Area (MCMA). The growth-rate of the total column around noon under low ventilation conditions is calculated and allows us to derive the average surface emission-flux at UNAM, while similar measurements taken at the edge of the MCMA in Tecámac provides information on background CO levels in the Mexico basin. Based on 3 yr of measurements, CO column measurements from the IASI satellite instrument are used to reconstruct the spatial distribution of this anthropogenic pollutant over the MCMA. The agreement between the measured columns of the satellite and ground-based measurements is excellent, particularly when a comparison strategy based on time-displaced air masses is used. The annual emission of the Mexico Megacity is estimated to be (2.15 ± 0.5) Tg yr−1 for the year 2008, while the official inventory for that year reported 1.6 Tg yr−1. The difference is slightly higher than the conservative uncertainty estimated in this work suggesting that the emission might be underestimated by the conventional bottom-up method. A larger discrepancy is found in the spatial distribution of the emissions, when comparing the emission flux over UNAM (derived from the ground-based measurement) with that of the inventory integrated over a representative area. The methodology presented here represents a new and useful strategy to evaluate the contribution of megacities to the global anthropogenic gas emissions. Additionally, three different strategies to compare ground and space-based measurements above an inhomogeneous and strongly contaminated area like Mexico City are presented and discussed.

The earthquake sequence in Friuli, Italy, 1976

1979 ◽  
Vol 69 (6) ◽  
pp. 1797-1818
Author(s):  
Vittorio Cagnetti ◽  
Vincenzo Pasquale
Keyword(s):  
Main Shock ◽  
Eastern Alps ◽  
Earthquake Sequence ◽  
Laboratory Studies ◽  
Fault Movement ◽  
Stress Changes ◽  
Entire Sequence ◽  
Strain Release ◽  
Largest Aftershock ◽  
Aftershock Region

abstract The seismic activity of the May 6, 1976 Friuli earthquake has been investigated. It provides clear evidence of internal clustering of shocks, with the largest aftershocks being followed by their own series of aftershocks. Late large aftershocks with their own aftershock series occurred 4 months after the main shock, when aftershocks had subsided. Thus, in the entire series of aftershocks, six phases of strain release are found, and part of the aftershock region is not included in the aftershock volume of the main shock. All this indicates that a few aftershocks are at least partially independent from the main shock. The value of b is estimated for the entire sequence and for the separate phases; during the activity, b shows an increase after the main shock, a decline immediately before the largest aftershock, and a second increase immediately afterward. This can be explained in terms of stress changes, and is consistent with laboratory studies of rock deformation. The compressive stress is perpendicular to the Eastern Alps, and may be considered as the principal cause of the earthquake sequence. The solution of the main shock of the sequence is a reversed fault movement, unlike most of the mechanisms in the focus of the earlier Friuli earthquakes which are of the transcurrent type.

scholarly journals Research on the Spatial Distribution Difference of Compulsory Education between China and Australia

2020 ◽  
Vol 15 (04) ◽  
pp. 129
Author(s):  
Saidong Lv ◽  
Yujun Pan
Keyword(s):  
Spatial Distribution ◽  
Regional Differences ◽  
Analytical Approach ◽  
Compulsory Education ◽  
Regional Data ◽  
Inductive Approach ◽  
Similarities And Differences ◽  
The Difference ◽  
Regional Imbalance ◽  
Analyze Data

This study collected regional data from 31 provinces in China and 8 states and territories in Australia in 2016. The study used the descriptive and analytical approach to analyze the results. Also, it used the inductive approach, the descriptive statics analysis and the SPSS to analyze data. it found that the distribution of compulsory education bears both similarities and differences in the two countries. In terms of similarities,there are certain regional differences in the teachers’ faculty of compulsory education in the two countries, and an unbalanced distribution of teachers has emerged. The difference is that although China's compulsory education has rqpidly, the teachers and funds of compulsory education lag far behind Australia, and the Regional imbalance is more serious in China than that in Australia.In other words, if there is a rapidly increasing population somewhere, and the nuers of teachers aren’t keeping up with this in China.

scholarly journals Entrenamiento para la mejora de disfunciones atencionales en niños y adolescentes con Síndrome de Asperger a través de estimulación cognitiva directa.

2016 ◽  
Vol 32 (2) ◽  
pp. 366 ◽  
Author(s):  
María-Ángeles Bravo-Alvarez ◽  
María Frontera-Sancho
Keyword(s):  
Training Program ◽  
Cognitive Stimulation ◽  
Attention Training ◽  
Large Magnitude ◽  
Psychometric Measures ◽  
M 12 ◽  
The Difference ◽  
Attentional Difficulties ◽  
Magnitude Difference ◽  
Moderate Magnitude

This research analyzes the generalization ability of learning in children and adolescents with Asperger Syndrome to attentional cognitive aspects with different demands on exercised through the use of a direct cognitive stimulation program. The sample consisted of 15 cases with Asperger between 7 and 15 years (M = 12, SD = 2.7) with attentional difficulties, measured by psychometric orientation instruments, to which an attention training program was implemented to two hours per week for six consecutive months. The results of the pretest-posttest analysis showed statistically significant differences in all attentional subsystems. Selective attention differences are moderate in variables related to processing speed, in sustained attention the reaction time significantly decreased (moderate magnitude of the difference) and increased the successes reducing errors (both with a large magnitude difference) . In alternating attention, a greater number of successes were observed and in split attention higher levels of total responses (both moderate magnitude) were obtained. It is concluded that the attentional performance in the cases analyzed improvement after applying a cognitive training program specifically being able to generalize learning psychometric measures.

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