Estimation of dip angle of fault or structural boundary by eigenvectors of gravity gradient tensors

Kusumoto, Shigekazu

doi:10.3124/segj.68.277

Cited by 6 publications

(17 citation statements)

References 44 publications

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“…We use the first HD, the first VD and the normalized total horizontal derivative (TDX) (Cooper and Cowan 2006), to detect structural boundaries, and also the dip angle (β) (Beiki 2013) and the dimensionality index (D i ) (Beiki and Pedersen 2010), as structural parameters to evaluate the subsurface fault structure (Kusumoto 2015). These derivatives and structural parameters are calculated from a gravity gradient tensor.…”

Section: Derivatives and Structural Parameters Calculated From A Gravmentioning

confidence: 99%

Continuity, segmentation and faulting type of active fault zones of the 2016 Kumamoto earthquake inferred from analyses of a gravity gradient tensor

Matsumoto

Hiramatsu

Sawada

2016

Earth Planets Space

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We analyze Bouguer anomalies in/around the focal region of the 2016 Kumamoto earthquake to examine features, such as continuity, segmentation and faulting type, of the active fault zones related to the earthquake. Several derivatives and structural parameters calculated from a gravity gradient tensor are applied to highlight the features. First horizontal and vertical derivatives, as well as a normalized total horizontal derivative, characterize well the continuous subsurface fault structure along the Futagawa fault zone. On the other hand, the Hinagu fault zone is not clearly detected by these derivatives, especially in the case of the Takano-Shirahata segment, suggesting a difference of cumulative vertical displacement between the two fault zones. The normalized total horizontal derivative and the dimensionality index indicate a discontinuity of the subsurface structure of the Hinagu fault zone, that is, a segment boundary between the Takano-Shirahata and the Hinagu segments. The aftershock distribution does not extend beyond this segment boundary. In other words, this segment boundary controls the southern end of the rupture area of the foreshock. We also recognize normal fault structures dipping to the northwest in some areas of the fault zones from estimations of dip angles.

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Section: Derivatives and Structural Parameters Calculated From A Gravmentioning

confidence: 99%

Continuity, segmentation and faulting type of active fault zones of the 2016 Kumamoto earthquake inferred from analyses of a gravity gradient tensor

Matsumoto

Hiramatsu

Sawada

2016

Earth Planets Space

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“…The dips of the Median Tectonic Line become low gradually to the north in the Beppu Bay area. Although Kusumoto (2015) reported that this dip estimation technique tends to underestimate the actual dip in deep parts when applied to normal faults, seismic reflection surveys have confirmed dips of normal faults distributed in Beppu Bay to be 17° and 7° by seismic reflection surveys (e.g. Itoh et al 2014).…”

Section: Resultsmentioning

confidence: 99%

“…4b) and applied this idea to analysis of fault dip. To effectively estimate the dip of the fault or density structure boundary, Kusumoto (2015) recommended that the estimation would be conducted at areas of high horizontal gravity gradient. In this study, the dip of the structure boundary was estimated in the area satisfying the conditions of which tectonic lines are extracted precisely and are 2-D structure, namely the areas of HG ≥ 25 E and DI ≤ 0.5.…”

Section: Dip Estimation Of Fault or Density Structure Boundarymentioning

confidence: 99%

“…In this paper, as a quick report, we show the dip distribution of the Oita-Kumamoto Tectonic Line estimated by the technique suggested by Beiki (2013) and Kusumoto (2015). With the exception of some geothermal areas, gravity gradiometry survey has not been conducted thus far in central Kyushu.…”

Section: Introductionmentioning

confidence: 99%

“…In the recent years, techniques estimating the dip of a geological structure boundary by using the gradient tensor of the potential fields have been developed and have shown good results (e.g. Beiki 2013;Kusumoto 2015Itoh et al 2016). The dip of the structure plays an important role in numerical simulations that quantitatively examine tectonics (e.g.…”

Section: Introductionmentioning

confidence: 99%

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Dip distribution of Oita–Kumamoto Tectonic Line located in central Kyushu, Japan, estimated by eigenvectors of gravity gradient tensor

Kusumoto

2016

Earth Planet Sp

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Abstract:We estimated the dip distribution of Oita-Kumamoto Tectonic Line located in central Kyushu, Japan, by using the dip of the maximum eigenvector of the gravity gradient tensor. A series of earthquakes in Kumamoto and Oita beginning on 14 April 2016 occurred along this tectonic line, the largest of which was M = 7.3. Because a gravity gradiometry survey has not been conducted in the study area, we calculated the gravity gradient tensor from the Bouguer gravity anomaly and employed it to the analysis. The general dip distribution of the Oita-Kumamoto Tectonic Line was found to be about 65° and tends to be higher towards its eastern end. In addition, we estimated the dip around the largest earthquake to be about 60° from the gravity gradient tensor. This result agrees with the dip of the earthquake source fault obtained by Global Navigation Satellite System data analysis.

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Gravity gradient tensor analysis to an active fault: a case study at the Togi-gawa Nangan fault, Noto Peninsula, central Japan

Hiramatsu

Sawada

Kobayashi

et al. 2019

Earth Planets Space

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Gravity gradient tensor analysis has been a powerful tool for investigating subsurface structures and recently its application to a two-dimensional fault structure has been developed. To elucidate the faulting type and spatial extent, specifically the continuity and the size, of the subsurface fault structure of an active fault through gravity gradient tensor analysis, we analyzed Bouguer anomalies, which were composed of dense gravity measurement data over the land and seafloor, and indices calculated from a gravity gradient tensor around the Togi-gawa Nangan fault (TNF), Noto Peninsula, central Japan. The features of Bouguer anomalies and their first horizontal and vertical derivatives demonstrate clearly that the TNF is a reverse fault dipping to the southeast. Furthermore, the combination of those derivatives and the dimensionality index revealed that the spatial extent of the subsurface fault structure is coincident with that of the surface fault trace and that it shows no evidence of connecting the TNF with surrounding active faults. Furthermore, the dip angle of the subsurface fault structure was estimated as 45°-60° from the minimum eigenvectors of the gravity gradient tensor. We confirmed that this result is coincident with the dip angle estimated using the two-dimensional Talwani's method. This high dip angle as a reverse fault suggests that the TNF has experienced inversion tectonics.

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Estimation of dip angle of fault or structural boundary by eigenvectors of gravity gradient tensors

Cited by 6 publications

References 44 publications

Continuity, segmentation and faulting type of active fault zones of the 2016 Kumamoto earthquake inferred from analyses of a gravity gradient tensor

Continuity, segmentation and faulting type of active fault zones of the 2016 Kumamoto earthquake inferred from analyses of a gravity gradient tensor

Dip distribution of Oita–Kumamoto Tectonic Line located in central Kyushu, Japan, estimated by eigenvectors of gravity gradient tensor

Gravity gradient tensor analysis to an active fault: a case study at the Togi-gawa Nangan fault, Noto Peninsula, central Japan

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