Fault plane of the 1964 Niigata earthquake, Japan, derived from relocation of the mainshock and aftershocks by using the modified joint hypocenter determination and grid search methods

Abstract The area of Sulawesi, especially along the Palu Koro Fault, is an area that is largely influenced by the confluence and movement of plates as well as regional fault activity pathways with high levels of seismicity. Determining the location of the hypocenter accurately through relocation is required in identifying the detailed tectonic structures in the area. Relocation of the hypocenter using the Modified Joint Hypocenter Determination (MJHD) method using the IASP91 velocity model in the period August to October 2018 with the arrival time data from BMKG catalog. The results of hypocenter relocation using the MJHD method show that from 132 earthquake distribution points to 63 earthquake hypocenter points after the relocation. The change in the location of the hypocenter was much denser along the Palu Koro Fault route than before the relocation as evidenced by the mean value of rms (root mean square) before relocation was 1.31 and after relocation it became smaller (0.61). Changes in parameter values after relocation using the MJHD method caused the distribution of the earthquake hypocenter to be tighter towards the Palu Koro fault than before the relocation, where the distribution had a random and scattered pattern.

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Seismicity and tectonics of western Venezuela

Bulletin of the Seismological Society of America ◽

10.1785/bssa0620061711 ◽

1972 ◽

Vol 62 (6) ◽

pp. 1711-1751 ◽

Cited By ~ 10

Author(s):

James W. Dewey

Keyword(s):

Fault Zone ◽

South American ◽

Seismic Zone ◽

South American Plate ◽

Intermediate Depth ◽

Hypocenter Determination ◽

Joint Hypocenter Determination ◽

Shallow Earthquakes ◽

Seismicity And Tectonics ◽

North And South

abstract New seismicity data on western Venezuela and northeastern Colombia are presented. Teleseismically recorded earthquakes from 1930 through 1970 have been relocated by Joint Hypocenter Determination (JHD) or with source-station adjustments calculated by JHD. Additionally, 540 days of recording have been obtained with local seismographs installed near the Boconó Fault. The most intense shallow activity occurred north and south of the Tachira Depression along the eastern flank of the Cordillera Oriental of Colombia. The Boconó Fault Zone is seismically active; small shallow shocks were recorded in it by the local stations. Shallow earthquakes also occur in the Cordillera de Mérida away from the Boconó Fault. The new hypocenters for the intermediate-depth Bucaramanga earthquakes define a smaller source volume than defined by previously computed hypocenters. A previously inferred southward-dipping seismic zone near Bucaramanga is probably spurious, a consequence of correlation between errors in latitude and errors in depth. If one assumes that these intermediate-depth earthquakes lie on a single lithospheric slab, that slab strikes approximately north and dips to the east. The distribution of hypocenters and focal mechanisms support the platetectonic hypothesis that the present tectonics of northwestern Venezuela are a result of eastward motion of the Caribbean plate with respect to the South American plate. The principal interface between these two plates may have changed within the last 5 m.y. from a zone of underthrusting west of the Sierra de Perija to the predominantly right-lateral Boconó Fault Zone.

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PMSVM: An Optimized Support Vector Machine Classification Algorithm Based on PCA and Multilevel Grid Search Methods

Mathematical Problems in Engineering ◽

10.1155/2015/320186 ◽

2015 ◽

Vol 2015 ◽

pp. 1-15 ◽

Cited By ~ 2

Author(s):

Yukai Yao ◽

Hongmei Cui ◽

Yang Liu ◽

Longjie Li ◽

Long Zhang ◽

...

Keyword(s):

Support Vector Machine ◽

Roc Curve ◽

Support Vector Machine Classifier ◽

Data Preprocessing ◽

Parameters Optimization ◽

Experimental Results ◽

Support Vector ◽

Grid Search ◽

Search Methods ◽

Sensitivity Specificity

We propose an optimized Support Vector Machine classifier, named PMSVM, in which System Normalization, PCA, and Multilevel Grid Search methods are comprehensively considered for data preprocessing and parameters optimization, respectively. The main goals of this study are to improve the classification efficiency and accuracy of SVM. Sensitivity, Specificity, Precision, and ROC curve, and so forth, are adopted to appraise the performances of PMSVM. Experimental results show that PMSVM has relatively better accuracy and remarkable higher efficiency compared with traditional SVM algorithms.

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Seismicity of the Baffin Bay region

Bulletin of the Seismological Society of America ◽

10.1785/bssa0640010087 ◽

1974 ◽

Vol 64 (1) ◽

pp. 87-98

Author(s):

Anthony Qamar

Keyword(s):

Upper Mantle ◽

Baffin Island ◽

Sea Floor ◽

Baffin Bay ◽

Hypocenter Determination ◽

Joint Hypocenter Determination ◽

Glacial Rebound ◽

Sea Floor Spreading ◽

Linear Trends ◽

Northeast Coast

abstract Twenty-eight earthquakes in the Baffin Bay region have been relocated using the method of Joint Hypocenter Determination. The revised locations indicate two parallel, linear trends, one along the northeast coast of Baffin Island and the other in the western part of Baffin Bay. The seismicity does not appear to be controlled by glacial rebound but may be a remnant of sea-floor spreading which occurred 40 to 60 m.y. ago. Early P arrivals at near seismograph stations (Δ < 20°) can be explained by a high-velocity (8.5 km/sec) upper mantle in the Baffin region.

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Seismicity of the Middle America arc-trench system near Managua, Nicaragua

Bulletin of the Seismological Society of America ◽

10.1785/bssa0640041033 ◽

1974 ◽

Vol 64 (4) ◽

pp. 1033-1048 ◽

Cited By ~ 5

Author(s):

James W. Dewey ◽

S. T. Algermissen

Keyword(s):

Surface Expression ◽

Benioff Zone ◽

Hypocenter Determination ◽

Joint Hypocenter Determination ◽

Volcanic Chain ◽

Middle America ◽

Master Event ◽

Shallow Focus ◽

Principal Chain ◽

East West

Abstract Hypocenters of earthquakes occurring during the period 1950 through 1972 in the Middle America arc-trench system near Managua, Nicaragua, have been relocated by the method of joint hypocenter determination (JHD) or the master event method with the Managua earthquake of December 23, 1972 as the calibration event. The relocated hypocenters show a considerably narrower Benioff zone than previous hypocenters of the same earthquakes and clearly separate shallow-focus volcanic terrane earthquakes of the type which struck Managua from the Benioff zone earthquakes. The shallow-focus volcanic terrane earthquakes are probably caused by tectonic conditions associated with the formation of the Nicaraguan depression or the principal chain of Quaternary volcanoes. The Managua earthquake of December 23, 1972 may have occurred as a consequence of slippage along a transform fault zone which connects offset segments of the chain of Quaternary volcanoes; the volcanic chain is then taken to be the surface expression of a secondary spreading zone which lies above the Benioff zone of the Middle America arc-trench system. Alternatively, the recent Managua earthquake may have occurred as a consequence of regional east-west tension in the Nicaraguan depression.

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