Krakatau caldera deposits: revisited and verification by geophysical means

One of the differences between volcanic craters and calderas is that the latter bottoms are flatways filled with caldera deposit with lower density in comparison to country rocks. The 1883 Krakatau eruption affords us important knowledge on caldera formation even if it was not observed with modern sophisticated instruments. First, volcanic activities of the Krakatau Islands before and after the 1883 eruption are reexamined: previous suppositions involving a caldera-forming eruption of the proto-Krakatau prior to 1883 proved to be unsupported by the bathymetric topographies and gravity anomalies on and around the Krakatau Islands. Then, Anak Krakatau is interpreted as a parasitic cone of the main Krakatau volcano. As supplementary knowledge to discussion of caldera deposits, the results of drillings at several calderas in Japan and Mexico are introduced. Mass deficiency of the caldera deposit at Krakatau caldera is estimated by the gravity anomaly observed there and converted to probable volume with suitable density. For quantitative examination of the subsurface structure beneath the Krakatau complex, spatial distributions of seismic S-wave attenuation and Vp/Vs ratios have been already studied by temporary seismological observations and their results have been published. The high ratios of Vp/Vs observed approximately at Krakatau caldera may be attributable to the caldera deposit that is low density and contain much water. As additional remarks, a zone having both the characters, S-wave attenuation and zones of relatively high Vp/Vs ratio, may be a probable magma reservoir centering at a depth of about 10 km.

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Measurement of seismic P- and S-wave attenuation in volcanic tuff, Rainier Mesa Tunnels, Nevada Test Site

Open-File Report ◽

10.3133/ofr94618 ◽

1994 ◽

Author(s):

R.D. Carroll

Keyword(s):

Wave Attenuation ◽

Test Site ◽

Nevada Test Site ◽

S Wave ◽

Volcanic Tuff

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Heterogeneities of the Field of S-Wave Attenuation in the Lithosphere of the Caucasus and Their Relationship with Seismicity

Izvestiya Atmospheric and Oceanic Physics ◽

10.1134/s0001433819100050 ◽

2019 ◽

Vol 55 (10) ◽

pp. 1526-1535

Author(s):

Yu. F. Kopnichev ◽

I. N. Sokolova

Keyword(s):

Wave Attenuation ◽

S Wave ◽

The Caucasus

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High Density and Low Density Lipoproteins in Chronic Renal Failure Before and After Renal Transplantation

Australian and New Zealand Journal of Medicine ◽

10.1111/j.1445-5994.1979.tb04316.x ◽

1979 ◽

Vol 9 (2) ◽

pp. 136-142 ◽

Cited By ~ 4

Author(s):

J. C. Gibson ◽

E. Savdiet ◽

L. A. Simons ◽

J. H. Stewart ◽

J. F. Mahonytt

Keyword(s):

Renal Failure ◽

Renal Transplantation ◽

Chronic Renal Failure ◽

Low Density Lipoproteins ◽

High Density ◽

Low Density ◽

Before And After

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S-wave attenuation in the Marmara Region, northwestern Turkey

Geophysical Research Letters ◽

10.1029/98gl02042 ◽

1998 ◽

Vol 25 (14) ◽

pp. 2733-2736 ◽

Cited By ~ 21

Author(s):

Horasan Gündüz ◽

Kaşlilar-Özcan Ayşe ◽

Boztepe-Güney Aysun ◽

Türkelli Niyazi

Keyword(s):

Wave Attenuation ◽

Marmara Region ◽

S Wave ◽

Northwestern Turkey

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P- and S-wave attenuation logs from monopole sonic data

Geophysics ◽

10.1190/1.1444774 ◽

2000 ◽

Vol 65 (3) ◽

pp. 755-765 ◽

Cited By ~ 37

Author(s):

Xinhua Sun ◽

Xiaoming Tang ◽

C. H. (Arthur) Cheng ◽

L. Neil Frazer

Keyword(s):

Wave Attenuation ◽

Fluid Velocity ◽

P Wave ◽

Reservoir Rock ◽

Rock Properties ◽

S Wave ◽

Intrinsic Attenuation ◽

Modified Method ◽

Receiver Array ◽

Attenuation Profiles

In this paper, a modification of an existing method for estimating relative P-wave attenuation is proposed. By generating synthetic waveforms without attenuation, the variation of geometrical spreading related to changes in formation properties with depth can be accounted for. With the modified method, reliable P- and S-wave attenuation logs can be extracted from monopole array acoustic waveform log data. Synthetic tests show that the P- and S-wave attenuation values estimated from synthetic waveforms agree well with their respective model values. In‐situ P- and S-wave attenuation profiles provide valuable information about reservoir rock properties. Field data processing results show that this method gives robust estimates of intrinsic attenuation. The attenuation profiles calculated independently from each waveform of an eight‐receiver array are consistent with one another. In fast formations where S-wave velocity exceeds the borehole fluid velocity, both P-wave attenuation ([Formula: see text]) and S-wave attenuation ([Formula: see text]) profiles can be obtained. P- and S-wave attenuation profiles and their comparisons are presented for three reservoirs. Their correlations with formation lithology, permeability, and fractures are also presented.

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S wave attenuation structure on the western side of the Nankai subduction zone: Implications for fluid distribution and dynamics

Journal of Geophysical Research Solid Earth ◽

10.1002/2014jb011103 ◽

2014 ◽

Vol 119 (10) ◽

pp. 7805-7822 ◽

Cited By ~ 3

Author(s):

Tsutomu Takahashi ◽

Koichiro Obana ◽

Yojiro Yamamoto ◽

Ayako Nakanishi ◽

Shuichi Kodaira ◽

...

Keyword(s):

Subduction Zone ◽

Wave Attenuation ◽

Fluid Distribution ◽

S Wave ◽

Nankai Subduction Zone ◽

Attenuation Structure ◽

Western Side

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Direct shear-wave seismic survey in Sanhu area, Qaidam Basin, west China

The Leading Edge ◽

10.1190/tle41010047.1 ◽

2022 ◽

Vol 41 (1) ◽

pp. 47-53

Author(s):

Zhiwen Deng ◽

Rui Zhang ◽

Liang Gou ◽

Shaohua Zhang ◽

Yuanyuan Yue ◽

...

Keyword(s):

Shear Wave ◽

Reservoir Characterization ◽

Qaidam Basin ◽

P Wave ◽

Data Sets ◽

Direct Shear ◽

Subsurface Structure ◽

S Wave ◽

West China ◽

Wave Data

The formation containing shallow gas clouds poses a major challenge for conventional P-wave seismic surveys in the Sanhu area, Qaidam Basin, west China, as it dramatically attenuates seismic P-waves, resulting in high uncertainty in the subsurface structure and complexity in reservoir characterization. To address this issue, we proposed a workflow of direct shear-wave seismic (S-S) surveys. This is because the shear wave is not significantly affected by the pore fluid. Our workflow includes acquisition, processing, and interpretation in calibration with conventional P-wave seismic data to obtain improved subsurface structure images and reservoir characterization. To procure a good S-wave seismic image, several key techniques were applied: (1) a newly developed S-wave vibrator, one of the most powerful such vibrators in the world, was used to send a strong S-wave into the subsurface; (2) the acquired 9C S-S data sets initially were rotated into SH-SH and SV-SV components and subsequently were rotated into fast and slow S-wave components; and (3) a surface-wave inversion technique was applied to obtain the near-surface shear-wave velocity, used for static correction. As expected, the S-wave data were not affected by the gas clouds. This allowed us to map the subsurface structures with stronger confidence than with the P-wave data. Such S-wave data materialize into similar frequency spectra as P-wave data with a better signal-to-noise ratio. Seismic attributes were also applied to the S-wave data sets. This resulted in clearly visible geologic features that were invisible in the P-wave data.

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Deciphering the 3-D distribution of fluid along the shallow Hikurangi subduction zone using P- and S-wave attenuation

Geophysical Journal International ◽

10.1093/gji/ggx348 ◽

2017 ◽

Vol 211 (2) ◽

pp. 1032-1045 ◽

Cited By ~ 12

Author(s):

Donna Eberhart-Phillips ◽

Stephen Bannister ◽

Martin Reyners

Keyword(s):

Subduction Zone ◽

Wave Attenuation ◽

S Wave

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Twin memory and twin amnesia in anorthoclase

Mineralogical Magazine ◽

10.1180/002646100549292 ◽

2000 ◽

Vol 64 (2) ◽

pp. 195-200 ◽

Cited By ~ 14

Author(s):

S. A. Hayward ◽

E. K. H. Salje

Keyword(s):

Phase Transitions ◽

Transition Temperature ◽

Alkali Feldspar ◽

Spatial Distributions ◽

X Ray Diffraction ◽

Alkali Cations ◽

X Ray ◽

Natural Minerals ◽

Synthetic Materials ◽

Before And After

AbstractMany natural minerals and synthetic materials display twin microstructures resulting from displacive phase transitions. These microstructures may be removed temporarily from the sample by heating above the relevant transition temperature, though the twinning generally returns on subsequent cooling.In anorthoclase, the spatial distributions of twins before and after brief annealing above TC are often identical. This property appears to be a common feature in many materials which undergo ferroelastic phase transitions, and is known as ‘twin memory’. The atomic mechanisms responsible for this twin memory may be investigated by studying the annealing regimes required to remove the memory effect; how long must a sample be annealed, and at what temperature, to induce ‘twin amnesia’.High-resolution X-ray diffraction (XRD) has been used to investigate twin memory and twin amnesia in anorthoclase. In anorthoclase, the primary constraint on twin amnesia is thermodynamic, rather than kinetic. The critical temperature to induce amnesia correlates well with the top of the (Na, K) solvus in disordered alkali feldspar. For this reason, the proposed mechanism for twin memory involves the segregation of alkali cations in thin lamellae at the twin boundaries.

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