Forecasts of earthquakes on the basis of complex geophysisical features

Sadovsky, M.A.; Nersesov, I. L.

doi:10.1016/0040-1951(74)90024-9

Cited by 18 publications

(12 citation statements)

References 3 publications

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“…In addition, a number of control parameters are also required to regulate the program operation. Detailed description of these parameters and the computational procedure can be found in Swanson (1988). Although the program solves for hypocentral locations of the input data set in addition to the velocity model parameters, we found that hypocentral determinations for a small subset of events scattered throughout the study area provided little new information on the overall spatial distribution of seismicity in the area.…”

Section: Methodsmentioning

confidence: 99%

“…The 'A', 'B', and 'C' grade events, which constitute under 50 per cent of each of the two data bases, are considered the most reliable for interpreting characteristics of spatial distribution of earthquake epicentres; the 'A' and 'B' grade events, approximately 25 per cent of the catalogues, are relied on for interpretation of the hypocentral depth distribution. Detailed descriptions of the earthquake location procedure and grading scheme are presented by Swanson (1988). The depth distributions for the 'A' and 'B' grade events, shown in Fig.…”

Section: Methodsmentioning

confidence: 99%

“…The data that provide the basis of this study are from the Complex Seismological Expedition (CSE) earthquake prediction laboratory at Garm, Tadjikistan, which has operated a local seismic network in one of the most active segments of the Central Asian seismic belt for nearly four decades (e.g. Sadovsky & Nersesov 1974;Guseva et al 1983;Pavlis, Hamburger & Nersesov 1989). In 1975, under the auspices of a cooperative program between the U S Geological Survey and the USSR Academy of Sciences, the CSE network was augmented by the establishment of a radio-telemetered seismic network, located in the axial portion of the Peter the First Range, the area of highest seismic activity in the Garm region.…”

Section: Introductionmentioning

confidence: 99%

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Velocity structure and seismicity of the Garm region, Central Asia

Hamburger

Swanson

Popandopulo

1993

Geophysical Journal International

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S U M M A R YWe have examined arrival-time data from two seismic networks operating within the Pamir-Tien Shan region of Central Asia in order to evaluate crustal structure and earthquake distribution in one of the most seismically active zones in the region. The data are from two networks surrounding the Soviet earthquake-prediction laboratory at Garm, Tadjikistan: a 15-station local network operated by the Soviet Complex Seismological Expedition (CSE) since the mid-l950s, and a dense telemetered network, nested within the larger CSE network, operated jointly by the US Geological Survey (USGS) and the CSE since 1975. A simultaneous inversion procedure was used to calculate l-D (layered) velocity models and station corrections independently for each of the two networks. Using a variety of data subsets and starting models, we obtained stable estimates of the velocity structure, independent of the initial velocity models. For both the CSE and the USGS network data the velocities of two upper-crustal layers proved to be indistinguishable from a model with a single layer over a half-space. For the CSE network, the best P-wave velocity model comprises an 8 km thick upper crustal layer of 5.2 km sK', overlying a 5.9 km s K ' half-space. Using data from the USGS network alone, a similar velocity model was obtained, with the exception of a significantly higher velocity (V, = 6.3 km sK ') for the mid-crustal half-space. These results contradict previously published velocity models featuring anomalously low or high seismic velocities in the upper to mid-crust. Hypocentral parameters were redetermined for approximately 26 000 events occurring during the period 1975-82 using the newly obtained velocity models and station corrections. Most of the seismicity in the study area is associated with active deformation of the sedimentary rocks of the Peter the First Range. The distribution of hypocentres within the range suggests the presence of a southeastdipping zone of seismicity that can be traced updip to the Petrovsky thrust fault. Beneath this upper crustal seismicity, at a depth of 12-17 km, is an aseismic zone that may be related to the presence of low-strength evaporites at the base of the sedimentary section. This aseismic zone is in turn underlain by anomalously deep crustal seismicity, at a depth of 17-30 km. The deeper seismicity appears to be associated with a southeast-dipping feature approximately 10 km in thickness. This dipping seismic zone is interpreted as a zone of intracontinental subduction, whose surface expression is the Vakhsh thrust fault, at the frontal edge of the Peter the First Range.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Velocity structure and seismicity of the Garm region, Central Asia

Hamburger

Swanson

Popandopulo

1993

Geophysical Journal International

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“…Moreover, those directions turned to 90º at two months or a little bit longer before the main shock [3][4][5]. Such phenomena were also observed in China.…”

Section: Introductionmentioning

confidence: 86%

Variation of Focal Parameters and Medium Characteristics During Small Earthquakes

Liu¹,

Liu²

2012

GEO

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In earthquake prediction, strong earthquakes are usually preceded by a series of small earthquakes. Thus, correct identification of those small earthquakes characteristics tell precursor observations and will lead to accurate prediction and judgement of impending main shocks. This paper discusses seismic source dynamic parameters, medium and rupture characteristics, and their variations during small earthquakes. Focal mechanism and its variation before and after main shock are also demonstrated along with several seismic examples to summarize the change of rupture characteristics (primary rupture direction, ambient shear stress, and waveform's temporal) and periodicity during small and medium earthquakes.

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“…Following reports of anomalous peaks in groundwater radon content before some earthquakes in the USSR (Ulomov & Mavashev 1971 ;Sadovsky 1974), a great deal of effort was made to extend such observations to other countries (e.g., King 1978King , 1980Wakita 1978;Teng 1980;Mogro-Campero et al 1980;Hauksson & Goddard 1981). Many precursory anomalies have been reported, both long-term (hundreds of days for magnitude 6 or more), and short-term (days or weeks).…”

Section: Introductionmentioning

confidence: 94%

An anomaly in borehole radon content at Wellington, New Zealand, in 1993

Robinson

1995

New Zealand Journal of Geology and Geophysics

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The radon content of the air in a 60 m deep well at Wellington has been monitored since 1978. The purpose is to test the proposal that anomalous radon content is a precursor to large local earthquakes. The data from 13 January 1990 to 31 July 1994 are homogeneous, free from data gaps, and have been corrected for air pressure and waterlevel changes. During this period there were eight large (magnitude 6.0 or more), shallow (depth <40 km), regional (distance of 800 km or less) earthquakes, but none closer than 172 km. The radon data show only a single anomalous period of 147 days (9% of the observation period) from 17 May to 10 October 1993 when the content was significantly higher than normal. Although two out of eight (25%) of the large, shallow, regional earthquakes occurred during this time, the evidence for a physical connection is weak, since this could happen with probability 0.15 for random earthquake occurrence times.

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Forecasts of earthquakes on the basis of complex geophysisical features

Cited by 18 publications

References 3 publications

Velocity structure and seismicity of the Garm region, Central Asia

Velocity structure and seismicity of the Garm region, Central Asia

Variation of Focal Parameters and Medium Characteristics During Small Earthquakes

An anomaly in borehole radon content at Wellington, New Zealand, in 1993

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