scholarly journals Quantitative mapping of precursory seismic quiescence before the 1989, M 7.1off-Sanriku earthquake, Japan

1999 ◽  
Vol 42 (5) ◽  
Author(s):  
M. Wyss ◽  
A. Hasegawa ◽  
S. Wiemer ◽  
N. Umino
Keyword(s):  
Main Shock ◽  
Time Window ◽  
Statistical Significance ◽  
Seismic Quiescence ◽  
Time And Space ◽  
Data Set ◽  
Rate Decrease ◽  
Aftershock Area ◽  
One Year ◽  
Precursory Seismic Quiescence

The first main shock of the off-Sanriku earthquake sequence (02/11/89, M 7.1; 18/07/92, M 6.9; 28/12/94, M 7.5) was preceded by a precursory seismic quiescence lasting 2.5 ± 1 year and up to this main shock. The detailed properties of this quiescence were mapped as a function of time and space by a gridding technique using the ZMAP computer code, and the statistical significance was estimated by generating a synthetic catalog based on the microearthquake catalog of Tohoku University, which was the data set used. The statistically most significant expression of this precursory quiescence has a probability of 0.1% to have occurred at random and was located in the eastern part of the 1989 aftershock area, at a point to which the 1994 aftershocks extended also. If we define the dimensions of the quiescence anomaly by a vertical cylinder with the depth of the entire seismogenic layer, centered at the point of most significant quiescence and showing a rate decrease of 75%, then we find its radius is 25 ± 9 km. If we allow other shapes, such as the simplified aftershock volume of 1989, or other simple geometric figures, to define the rate decrease we find dimensions of 80 by 80 km. The characteristics of the quiescence anomaly do not depend strongly on the choice of free parameters within the following ranges: 100 ? number of events ? 400, 2.0 ? Mmin £ 3.0, 1 ? time window ? 3 years. With our method, a thorough analysis of the period before the 1994 main shock is not possible because of the interference of the extended aftershock sequence of 1989. Nevertheless, we identified a quiescence of nearly zero earthquakes located near the center of the 1994 aftershock area that lasted for one year up to that main shock. However, this quiescence period ranked only 46th in significance, behind other quiescences of equal duration and similar dimensions distributed in time and space through the data set. Because of the ubiquitous existence of periods of near zero activity during short periods like one year, we find that quiescences shorter than about 1.5 years cannot be defined with high statistical significance in most earthquake catalogs. In the last two years of the data (1995.3-1997.3) we see no extensive quiescence of high significance off the east coast of Honshu between 36.5° and 42°N in the currently available data.

Seismicity rate change before the Irpinia (M = 6.9) 1980 earthquake

1997 ◽  
Vol 87 (2) ◽  
pp. 318-326 ◽  
Author(s):  
M. Wyss ◽  
R. Console ◽  
M. Murru
Keyword(s):  
Southern Italy ◽  
Seismic Quiescence ◽  
Magnitude Scale ◽  
Data Sets ◽  
Data Set ◽  
Background Rate ◽  
Seismicity Rate ◽  
Rupture Area ◽  
The Stability ◽  
Precursory Seismic Quiescence

Abstract The stability of seismicity rate in central and southern Italy was examined in two data sets: from 1975.0 to 1995.0 with M ≧ 3.4 and from 1987.5 to 1996.0 with M ≧ 2.5. These are the approximate minimum magnitudes of complete reporting for the respective periods. The first set was used to evaluate the possibility that the 23 November 1980 Irpinia (M 6.9) earthquake was preceded by precursory seismic quiescence; the second was used to evaluate the conditions under which a current seismic quiescence could be detected in central or southern Italy. During the years before the Irpinia earthquake, the seismicity rate in the northern half of the rupture area and north of it was low. Whether this was a case of precursory quiescence or not is subject to interpretation because the background rate cannot be established for the years before 1975. If we accept the relatively constant seismicity rate in the Irpinia volume during the decade after the mainshock as representative for the background rate, we have a clear case of precursory quiescence lasting at least 1.3 yr up to the mainshock. Alternatively, it can be postulated that the seismicity rate during the decade following this shock was elevated regionally because of the stress redistribution and that the low rates seen before it represent the normal background rate. Even if this reasoning is accepted, the fact remains that a volume including the northern part of the rupture produced no M ≧ 3.4 earthquakes during 1.3 yr before the Irpinia earthquake but produced 10 earthquakes during the 4.7 previous yr. Given these facts, we favor the interpretation that the Irpinia 1980 earthquake was preceded by precursory seismic quiescence. In the entire data set, there are three other cases of quiescence of higher significance without a mainshock following. Since no other mainshock with M > 6 exists in the data set, no missed event exists. We propose that in Italy precursory seismic quiescence may precede mainshocks and that it may be detected in the future by the improved catalog of the modern data set beginning in 1987.5. Major magnitude scale changes give the mistaken appearance that fewer large-magnitude earthquakes occur in Italy now than in years before 1987. We postulate that the rate of earthquakes has not changed and that the magnitude scale should be adjusted.

scholarly journals Do galactic bars depend on environment?: an information theoretic analysis of Galaxy Zoo 2

2020 ◽  
Vol 501 (1) ◽  
pp. 994-1001
Author(s):  
Suman Sarkar ◽  
Biswajit Pandey ◽  
Snehasish Bhattacharjee
Keyword(s):  
Spatial Distribution ◽  
Mutual Information ◽  
Local Density ◽  
Statistical Significance ◽  
Distribution Functions ◽  
Cumulative Distribution ◽  
Host Galaxy ◽  
Data Sets ◽  
Data Set ◽  
Information Theoretic

ABSTRACT We use an information theoretic framework to analyse data from the Galaxy Zoo 2 project and study if there are any statistically significant correlations between the presence of bars in spiral galaxies and their environment. We measure the mutual information between the barredness of galaxies and their environments in a volume limited sample (Mr ≤ −21) and compare it with the same in data sets where (i) the bar/unbar classifications are randomized and (ii) the spatial distribution of galaxies are shuffled on different length scales. We assess the statistical significance of the differences in the mutual information using a t-test and find that both randomization of morphological classifications and shuffling of spatial distribution do not alter the mutual information in a statistically significant way. The non-zero mutual information between the barredness and environment arises due to the finite and discrete nature of the data set that can be entirely explained by mock Poisson distributions. We also separately compare the cumulative distribution functions of the barred and unbarred galaxies as a function of their local density. Using a Kolmogorov–Smirnov test, we find that the null hypothesis cannot be rejected even at $75{{\ \rm per\ cent}}$ confidence level. Our analysis indicates that environments do not play a significant role in the formation of a bar, which is largely determined by the internal processes of the host galaxy.

scholarly journals Seismic Damage Accumulation in Highway Bridges in Earthquake-Prone Regions

2015 ◽  
Vol 31 (1) ◽  
pp. 115-135 ◽  
Author(s):  
Jayadipta Ghosh ◽  
Jamie E. Padgett ◽  
Mauricio Sánchez-Silva
Keyword(s):  
Service Life ◽  
Damage Accumulation ◽  
Main Shock ◽  
Prediction Models ◽  
Time Window ◽  
Damage Index ◽  
Active Regions ◽  
Highway Bridges ◽  
Main Shocks ◽  
Aftershock Sequences

Civil infrastructures, such as highway bridges, located in seismically active regions are often subjected to multiple earthquakes, including multiple main shocks during their service life or main shock–aftershock sequences. Repeated seismic events result in reduced structural capacity and may lead to bridge collapse, causing disruption in the normal functioning of transportation networks. This study proposes a framework to predict damage accumulation in structures subjected to multiple shock scenarios after developing damage index prediction models and accounting for the probabilistic nature of the hazard. The versatility of the proposed framework is demonstrated on a case-study highway bridge located in California for two distinct hazard scenarios: (1) multiple main shocks during the service life and (2) multiple aftershock earthquake occurrences following a single main shock. Results reveal that in both cases there is a significant increase in damage index exceedance probabilities due to repeated shocks within the time window of interest.

Moment-tensor solutions for the 24 November 1987 Superstition Hills, California, earthquakes

1989 ◽  
Vol 79 (2) ◽  
pp. 493-499
Author(s):  
Stuart A. Sipkin
Keyword(s):  
Main Shock ◽  
Moment Tensor ◽  
Time Dependent ◽  
Origin Time ◽  
Data Set ◽  
Filter Theory ◽  
Long Period ◽  
Seismograph Network ◽  
Scalar Moment

Abstract The teleseismic long-period waveforms recorded by the Global Digital Seismograph Network from the two largest Superstition Hills earthquakes are inverted using an algorithm based on optimal filter theory. These solutions differ slightly from those published in the Preliminary Determination of Epicenters Monthly Listing because a somewhat different, improved data set was used in the inversions and a time-dependent moment-tensor algorithm was used to investigate the complexity of the main shock. The foreshock (origin time 01:54:14.5, mb 5.7, Ms 6.2) had a scalar moment of 2.3 × 1025 dyne-cm, a depth of 8 km, and a mechanism of strike 217°, dip 79°, rake 4°. The main shock (origin time 13:15:56.4, mb 6.0, Ms 6.6) was a complex event, consisting of at least two subevents, with a combined scalar moment of 1.0 × 1026 dyne-cm, a depth of 10 km, and a mechanism of strike 303°, dip 89°, rake −180°.

Seismic quiescence, stress drops, and asperities in the New Hebrides arc

1983 ◽  
Vol 73 (1) ◽  
pp. 219-236
Author(s):  
M. Wyss ◽  
R. E. Habermann ◽  
Ch. Heiniger
Keyword(s):  
High Stress ◽  
Plate Boundary ◽  
Seismic Quiescence ◽  
Data Set ◽  
Seismicity Rate ◽  
Seismic Gaps ◽  
Main Shocks ◽  
Seismicity Rates ◽  
New Hebrides ◽  
Stress Drops

abstract The rate of occurrence of earthquakes shallower than 100 km during the years 1963 to 1980 was studied as a function of time and space along the New Hebrides island arc. Systematic examination of the seismicity rates for different magnitude bands showed that events with mb < 4.8 were not reported consistently over time. The seismicity rate as defined by mb ≧ 4.8 events was examined quantitatively and systematically in the source volumes of three recent main shocks and within two seismic gaps. A clear case of seismic quiescence could be shown to have existed before one of the large main shocks if a major asperity was excluded from the volume studied. The 1980 Ms = 8 rupture in the northern New Hebrides was preceded by a pattern of 9 to 12 yr of quiescence followed by 5 yr of normal rate. This pattern does not conform to the hypothesis that quiescence lasts up to the mainshock which it precedes. The 1980 rupture also did not fully conform to the gap hypothesis: half of its aftershock area covered part of a great rupture which occurred in 1966. A major asperity seemed to play a critical role in the 1966 and 1980 great ruptures: it stopped the 1966 rupture, and both parts of the 1980 double rupture initiated from it. In addition, this major asperity made itself known by a seismicity rate and stress drops higher than in the surrounding areas. Stress drops of 272 earthquakes were estimated by the MS/mb method. Time dependence of stress drops could not be studied because of changes in the world data set of Ms and mb values. Areas of high stress drops did not correlate in general with areas of high seismicity rate. Instead, outstandingly high average stress drops were observed in two plate boundary segments with average seismicity rate where ocean floor ridges are being subducted. The seismic gaps of the central and northern New Hebrides each contain seismically quiet regions. In the central New Hebrides, the 50 to 100 km of the plate boundary near 18.5°S showed an extremely low seismicity rate during the entire observation period. Low seismicity could be a permanent property of this location. In the northern New Hebrides gap, seismic quiescence started in mid-1972, except in a central volume where high stress drops are observed. This volume is interpreted as an asperity, and the quiescence may be interpreted as part of the preparation process to a future large main shock near 13.5°S.

GAIT SPEED AND HANDGRIP STRENGTH AS PREDICTORS OF INCIDENT DISABILITY IN MEXICAN OLDER ADULTS

2014 ◽  
pp. 1-4
Author(s):  
T. LOPEZ-TEROS ◽  
L.M. GUTIERREZ-ROBLEDO ◽  
M.U. PEREZ-ZEPEDA
Keyword(s):  
Older Adults ◽  
Gait Speed ◽  
Daily Living ◽  
Handgrip Strength ◽  
Statistical Significance ◽  
Adverse Outcomes ◽  
Community Dwelling ◽  
Performance Tests ◽  
One Year

Physical performance tests are associated with different adverse outcomes in older people. Theobjective of this study was to test the association between handgrip strength and gait speed with incidentdisability in community-dwelling, well-functioning, Mexican older adults (age ≥70 years). Incident disability wasdefined as the onset of any difficulty in basic or instrumental activities of daily living. Of a total of 133participants, 52.6% (n=70) experienced incident disability during one year of follow-up. Significant associationsof handgrip strength (odds ratio [OR] 0.96, 95% confidence interval [95%CI] 0.93-0.99) and gait speed (OR0.27, 95%CI 0.07-0.99) with incident disability were reported. The inclusion of covariates in the models reducedthe statistical significance of the associations without substantially modifying the magnitude of them. Handgripstrength and gait speed are independently associated with incident disability in Mexican older adults.

Abstract 3097: Acute In-hospital Stroke: How Do We Do Compared To Strokes In The Emergency Department?

Stroke ◽  
2012 ◽  
Vol 43 (suppl_1) ◽  
Author(s):  
Dolora Wisco ◽  
Christopher Newey ◽  
Pravin George ◽  
James Gebel
Keyword(s):  
Emergency Department ◽  
Time Window ◽  
Stroke Treatment ◽  
Intravenous Tissue Plasminogen Activator ◽  
Tertiary Center ◽  
Neuro Imaging ◽  
One Year ◽  
To Receive ◽  
Iv Tpa ◽  
Arterial Thrombolysis

Introduction: Intravenous tissue plasminogen activator (IV tPA) has been approved for treating strokes up to 3 hours after onset of symptoms and may be beneficial up to 4.5 hours in patients who qualify. Additionally, neuro-intervention, i.e., intra-arterial thrombolysis or thrombectomy, is also an approved treatment option. Population studies show that 6% receive IV tPA within 3 hours of stroke onset. However, in-hospital strokes present challenges to treating within an adequate time. We present here our experience with in-hospital strokes, treatments, and identifiable delays in treatments. Methods: Single, tertiary center retrospective study of 55 in-hospital strokes over a one-year period from January 2009 to January 2010, and strokes in the Emergency Department over 6 month period from January 2010 to June 2010. Results: Twenty-nine in-hospital strokes were evaluated within 3 hours of symptoms onset. Two (6.9%) received IV tPA, and four (13.8%) received neuro-intervention (either intra-arterial thrombolysis or thrombectomy). None of the patients who presented greater than 3 hours after symptom onset was treated with any treatment (n=28). When compared to patients who present to the ED within 3 hours, in-hospital strokes were less likely to get IV tPA (6.9% vs. 20.8%), and they were more likely to receive neuro-intervention (13.8% vs. 10.3%). Neuro-intervention was performed on 9.09% of all in-hospital strokes (1 of 5 presented beyond the 3 hour time window). For in-hospital strokes that receive any treatment within 3 hours, the average time to neurology evaluation, to CT, and to treatment are 35 min, 68 min, and 237 min, respectively. For strokes in the Ed, the average time to evaluation, to CT, and to treatment are 90 min, 28 min, and 66 min respectively. The delay for in-hospital strokes is in obtaining the CT and initiating the treatment. Discussion: In-hospital stroke patients wait longer than their ED counterparts to be taken to CT and to receive stroke treatment. They are also less likely to receive IV tPA, and more likely to receive neuro-intervention. The longer time to neuro-imaging and thrombolytic treatment may reflect the fact that patients suffering in-hospital strokes have more complex medical co-morbidities that must be taken account during the evaluation and administration of thrombolytic therapy.

scholarly journals Studies on mosquitoes (Diptera: Culicidae) and anthropic environment: 1- Parity of blood seeking Anopheles (Kerteszia) in South-Eastern Brazil

1993 ◽  
Vol 27 (1) ◽  
pp. 1-8 ◽  
Author(s):  
Oswaldo Paulo Forattini ◽  
Iná Kakitani ◽  
Eduardo Massad ◽  
Almério de Castro Gomes
Keyword(s):  
Statistical Significance ◽  
Abundant Species ◽  
Common Pattern ◽  
Host Seeking ◽  
Eastern Brazil ◽  
High Statistical Significance ◽  
Age Grading ◽  
One Year ◽  
Anopheles Cruzii ◽  
Indoor And Outdoor

Populations of Anopheles (Kerteszia) were sampled fortnightly over a one-year period (August 1991 to July 1992) at Ribeira Valley, S. Paulo State, Brazil. Indoor and outdoor collections were made on human bait at evening crepuscular period. The Polovodova technique for age grading was applied to 3,501 females of Anopheles cruzii and to 416 females of An. bellator. That sample represented 34.4% of the total number of mosquitoes collected. The most abundant species found was An. cruzii. However, An. bellator showed an endophagy that was almost three times greater than that of An. cruzii. The overall parous rate was 25.4% and uniparity was practically dominant one. A proportion of 26.9% of An. cruzii and 12.0% of An. bellator were found to be uniparous. Only three outdoor females of the former species (0.1%) showed biparity. Parity of An. cruzii was higher in females caught outdoors than in those caught indoors. Nevertheless, 497 nulliparous females examined (417 cruzii and 80 bellator) had ovaries that had advanced to Christophers and Mer stages III to V. These results imply that these females had already practised hematophagy. Relating these results to those from the parous females, a high statistical significance was found, leading to the conclusion that gonothophic discordance is a common pattern among these anophelines. Further, these results obtained with human bait catches strongly suggest that nearly 38.0% of these host-seeking females had already taken at least one previous blood-meal. So it is possible that enough time could thus be available for the plasmodian development in the vectors.

scholarly journals Children with 5′-end NF1 gene mutations are more likely to have glioma

2017 ◽  
Vol 3 (5) ◽  
pp. e192 ◽  
Author(s):  
Corina Anastasaki ◽  
Stephanie M. Morris ◽  
Feng Gao ◽  
David H. Gutmann
Keyword(s):  
Gene Mutation ◽  
Statistical Significance ◽  
Gene Mutations ◽  
Neurofibromatosis Type ◽  
Published Data ◽  
Data Sets ◽  
Nonsense Mutations ◽  
Data Set ◽  
Nf1 Gene ◽  
The Relationship

Objective:To ascertain the relationship between the germline NF1 gene mutation and glioma development in patients with neurofibromatosis type 1 (NF1).Methods:The relationship between the type and location of the germline NF1 mutation and the presence of a glioma was analyzed in 37 participants with NF1 from one institution (Washington University School of Medicine [WUSM]) with a clinical diagnosis of NF1. Odds ratios (ORs) were calculated using both unadjusted and weighted analyses of this data set in combination with 4 previously published data sets.Results:While no statistical significance was observed between the location and type of the NF1 mutation and glioma in the WUSM cohort, power calculations revealed that a sample size of 307 participants would be required to determine the predictive value of the position or type of the NF1 gene mutation. Combining our data set with 4 previously published data sets (n = 310), children with glioma were found to be more likely to harbor 5′-end gene mutations (OR = 2; p = 0.006). Moreover, while not clinically predictive due to insufficient sensitivity and specificity, this association with glioma was stronger for participants with 5′-end truncating (OR = 2.32; p = 0.005) or 5′-end nonsense (OR = 3.93; p = 0.005) mutations relative to those without glioma.Conclusions:Individuals with NF1 and glioma are more likely to harbor nonsense mutations in the 5′ end of the NF1 gene, suggesting that the NF1 mutation may be one predictive factor for glioma in this at-risk population.

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