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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 123 (1995), S. 0 
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: The seismicity rate in the Mudurnu Valley of Turkey was studied using an earthquake catalogue that reports events homogeneously down to magnitude 2.3 for the years 1985–1989, and covers the area between latitudes 40.2° and 41.0°N, and longitudes 30.0° and 31.5°E. During this period the only two main shocks, M= 4.0 and M= 4.3, occurred on 1988 September 6 and 1988 December 9 within about 30km of each other. A highly significant seismic quiescence is evident in the area surrounding these main shocks, while the seismicity rate in the rest of the area covered by the catalogue remains constant. the quiescence becomes more pronounced the smaller the area around the main shocks that is studied. the smallest areas that can be studied contain about 60 earthquakes and have dimensions of approximately 25km on each side. the decreases in seismicity rates are 50–80 per cent depending on the volume and period used for defining the quiescence. the quiescence started in 1988 January and lasted about seven months, with approximately 4.5 months of normal activity separating it from the main shock of December. the precursor time of 12 months for an M= 4.3 main shock is similar to those observed in California. It is concluded that it is possible to resolve precursory quiescence before moderate and large earthquakes in the Mudurnu area with the existing seismograph network.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 127 (1996), S. 0 
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: A highly significant seismic quiescence with a standard deviate Z = 10.1. corresponding to a 99 per cent confidence level, lasted from 1987.7 up to the 1990 February 20 Izu-Oshima M 6.5 earthquake. The quiescent volume had dimensions of 30 km N-S and 10 km E-W and was centred below 14 km depth. Within the recently upgraded seismograph network of the Earthquake Research Institute (ERI), this main shock was the only one with a magnitude M 〉 5.8 in the upper 30 km of the crust for which the precursory quiescence hypothesis could be tested. Within a radius of 50 km, and during the observation period (1983.5–1995.9), there were no other 1.5 yr or longer periods of quiescence that were rated Z 〉 6.5 in the declustered earthquake catalogue, except one that was associated with volcanic activity. The total space-time covered by alarms, including the volcanic one, was less than 1 per cent at the Z = 6.5 level. The rarity of highly significant episodes of quiescence, and the correlation in space and time suggest that a precursory seismic quiescence started 2.5 yr before the Izu-Oshima 1990 earthquake in its source volume and to the north of it, and that it can be recognized with an alarm level of Z = 6.0, generating no false alarms. During the 1.5 yr quiescence window, only 10 earthquakes occurred in the quiet volume, whereas 50 events were expected based on the rate seen at other times. In randomly selected volumes containing 50, 100 and 200 events, the anomaly scored Z = 6.1 to 10.1. On the basis of the data from May 1983 to 1995, there is no highly significant quiescence currently present in the Izu-Oshima area.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 110 (1992), S. 0 
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: The Parkfield segment of the San Andreas fault shows seismic quiescence for M 〉 2.0 earthquakes since early to mid-1986. The rate decreases by 45 to 70 per cent depending on the magnitude band. We interpret this change as real because it is concentrated in the larger magnitudes and cannot be explained by a reasonable magnitude shift. The rate decrease is present in the Parkfield segment of the fault between 35.6 and 36.1°N, and no other rate change as significant has been observed during the time when high quality data were available (since 1975). We interpret this observation as a seismic quiescence precursor to the next Parkfield mainshock. Although information on the expected duration of precursory quiescence is weak, we estimate that the Parkfield earthquake should occur in the interval 1990 February to 1992 February. Precursory seismic quiescence, which lasted approximately 1.5 yr, was found in, and possibly around, the source volume of an earthquake withM= 3.6 which occurred on 1986 August 29 in the Parkfield area. This observation demonstrates that the quiescence hypothesis is applicable to the Parkfield segment of the San Andreas fault.The false alarm rate was estimated in a detailed analysis as a function of alarm level for the fault segments surrounding the M= 5.0 Stone Canyon (1982 August) and M= 3.6 Parkfield (1986 August) mainshocks. For these two events, the duration and statistical significance of false alarms as a function of space, time and magnitude band was determined. We propose that in this tectonic environment, and with the data characteristics of these earthquake catalogues, attempts to predict mainshocks based on the quiescence hypothesis may be successful and generate one to two false alarms covering about 10 per cent of the time-space dimensions of the catalogue.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 266 (1977), S. 805-808 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The 25-cm uplift in Southern California is interpreted as being due to dilatancy of the crust, which started in 1961 along the San Andreas fault and spread laterally during 1964–69. The San Fernando earthquake of 1971 occurred in part of the dilatant volume, and is interpreted as a sideshow ...
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1420-9136
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Conclusions Several cases of extremely strong quiescences have been investigated in great detail, and it was found that they are statistically highly significant and that they cannot be reasonably explained by catalog heterogeneity. Several additional cases of quantitatively measured quiescence have been documented. The method of measuring quiescence has progressed from using visual means to using a quantitative approach, and the understanding of the noise sources has significantly advanced during the last few years. Therefore I feel that quiescence is a real phenomenon and the method to detect it has matured to a point that is acceptable for the List of Significant Precursors, although considerably more work needs to be done to understand this parameter and its role in the earthquake generation process.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Pure and applied geophysics 149 (1997), S. 1-2 
    ISSN: 1420-9136
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Pure and applied geophysics 149 (1997), S. 3-16 
    ISSN: 1420-9136
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract This review summarizes the result of the second round of nominations for the IASPEI Preliminary List of Significant Precursors. Currently this List contains five cases of precursors: (1) foreshocks, (2) preshocks, (3) seismic quiescence before major aftershocks, (4) radon decrease in ground water, and (5) ground water level increase. A list of four cases that could not be accepted nor rejected by the panels reviewing them contains three on crustal deformations and one on seismic quiescence. In the second round 10 nominations were evaluated, nine new ones and one which had been considered previously. Two were accepted for the List, two were placed in the category of undecided cases. To date, a total of 40 nominations have been evaluated by IASPEI. For 37 of these the nominations, the mail reviews, the panel opinions, and, where supplied, the author's reply were published. This evaluation process remains active throughout the International Decade for Natural Hazards Reduction. Additional nominations are invited. The IASPEI Sub-commission on Earthquake Prediction does not guarantee that precursors accepted for the List can be used for earthquake prediction, nor does rejection of a nomination mean that the particular method could never become useful for prediction. However, the List, as well as the interchanges between authors and reviewers, allow us to gauge the state-of-the-art in earthquake prediction research. It is clear that we do not have an earthquake prediction capability, because the manner in which to use the few precursors on the List for predictions is not known. It also appears that many of the results thought to be conclusive by the authors, may not command the respect of the seismological research community at large. A more quantitative approach to data analysis, the use of rigorous statistical techniques, and high quality, long-term data sets are needed to make progress in earthquake prediction research.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 329 (1987), S. 323-325 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The hypothesis that quiescence precedes large mainshocks2"4 is supported by 13 cases from areas other than the San Andreas fault, in which decreases in precursory rate have been measured quantitatively. The mainshock magnitudes range from 6.3 to 8.0, with shorter durations of quiescence for the ...
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 345 (1990), S. 290-290 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] UNTIL now it has seemed reasonable to model the seismic cycle of great earthquakes along plate boundaries as follows: at the time of a great earthquake a rupture with approximately uniform slip releases most of the available energy throughout the extent of the rupture outlined by the aftershocks. ...
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 242 (1973), S. 255-256 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] From hypocentre locations, the thickness of the seismic zone has been estimated to be at most 25 km in the Tonga area6'7 and approximately 10 km in Southern Alaska8 and the Central Aleutians9. Because the hypocentre determina-tions are still affected by considerable errors it has been sug-gested6-7 ...
    Type of Medium: Electronic Resource
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