scholarly journals Subsurface basement structure inferred from resistivity and gravity data around the Muramatsu active fault, the eastern margin of the Niigata sedimentary basin, central Japan

2007 ◽  
Vol 72 (4) ◽  
pp. 321-332
Author(s):  
Masami Otake ◽  
Atsushi Momose ◽  
Susumu Endo ◽  
Takashi Kaneko
Keyword(s):  
Active Fault ◽  
Sedimentary Basin ◽  
Gravity Data ◽  
Central Japan ◽  
Basement Structure ◽  
Eastern Margin

scholarly journals Basin Depth Mapping Beneath Wellington City Based on Residual Gravity Anomalies

2021 ◽  
Author(s):  
◽  
Alistair Stronach
Keyword(s):  
Gravity Anomaly ◽  
Sedimentary Basin ◽  
Gravity Data ◽  
Three Dimensional ◽  
Maximum Amplitude ◽  
Central Business District ◽  
Gravity Anomalies ◽  
Depth Map ◽  
Capital City ◽  
Detailed Knowledge

<p><b>New Zealand’s capital city of Wellington lies in an area of high seismic risk, which is further increased by the sedimentary basin beneath the Central Business District (CBD). Ground motion data and damage patterns from the 2013 Cook Strait and 2016 Kaikōura earthquakes indicate that two- and three-dimensional amplification effects due to the Wellington sedimentary basin may be significant. These effects are not currently accounted for in the New Zealand Building Code. In order for this to be done, three-dimensional simulations of earthquake shaking need to be undertaken, which requires detailed knowledge of basin geometry. This is currently lacking, primarily because of a dearth of deep boreholes in the CBD area, particularly in Thorndon and Pipitea where sediment depths are estimated to be greatest.</b></p> <p>A new basin depth map for the Wellington CBD has been created by conducting a gravity survey using a modern Scintrex CG-6 gravity meter. Across the study area, 519 new high precision gravity measurements were made and a residual anomaly map created, showing a maximum amplitude anomaly of -6.2 mGal with uncertainties better than ±0.1 mGal. Thirteen two-dimensional geological profiles were modelled to fit the anomalies, then combined with existing borehole constraints to construct the basin depth map. </p> <p>Results indicate on average greater depths than in existing models, particularly in Pipitea where depths are interpreted to be as great as 450 m, a difference of 250 m. Within 1 km of shore depths are interpreted to increase further, to 600 m. The recently discovered basin bounding Aotea Fault is resolved in the gravity data, where the basement is offset by up to 13 m, gravity anomaly gradients up to 8 mGal/km are observed, and possible multiple fault strands identified. A secondary strand of the Wellington Fault is also identified in the north of Pipitea, where gravity anomaly gradients up to 18 mGal/km are observed.</p>

A GRAVITY MAXIMUM IN THE GREAT VALLEY OF CALIFORNIA DUE TO THE ISOSTATIC EFFECT OF THE SIERRA NEVADA

Geophysics ◽  
1957 ◽  
Vol 22 (1) ◽  
pp. 62-66 ◽  
Author(s):  
L. F. Ivanhoe
Keyword(s):  
Sierra Nevada ◽  
Sedimentary Basin ◽  
Gravity Data ◽  
Full Length ◽  
Gravity Effect ◽  
Great Valley

A gravity maximum extends along the full length of the Great Valley of California. This feature is believed to represent the western limit of the gravity effect due to the adjustment of the Sierra Nevada isostatic block. Recognition that such a maximum with a sedimentary basin may be due to isostasy rather than to shallow geologic features assists in the interpretation of gravity data.

scholarly journals Estimation of Paleo-Seismicity in the Nobi Active Fault System, Central Japan. Excavation Study of the Umehara Fault, Central Strand in the Nobi Active Fault System.

1992 ◽  
Vol 101 (1) ◽  
pp. 1-18 ◽  
Author(s):  
Atsumasa OKADA ◽  
Mitsuhisa WATANABE ◽  
Masataka ANDO ◽  
Tameshige TSUKUDA ◽  
Shin'ichi HIRANO
Keyword(s):  
Active Fault ◽  
Fault System ◽  
Central Japan ◽  
Central Strand
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