Jun Matsushima

Seismic wave attenuation in methane hydrate‐bearing sediments: Vertical seismic profiling data from the Nankai Trough exploratory well, offshore Tokai, central Japan

[1] Data from two vertical seismic profiles (VSPs) from the Nankai Trough exploratory well, offshore Tokai, central Japan, are used to estimate compressional attenuation in methane hydrate (MH)-bearing sediments at seismic frequencies of 30-110 Hz. We compare spectral ratio and centroid frequency shift methods for measuring attenuation. To isolate intrinsic attenuation from total attenuation, attenuation is computed from multiples using one-dimensional synthetic VSP data from sonic and density logs. The use of two different measurement methods and two VSPs recorded at just 100 m separation provides an opportunity to validate the attenuation measurements. No significant compressional attenuation was observed in MH-bearing sediments at seismic frequencies. Macroscopically, the peaks of highest attenuation in the seismic frequency range correspond to low-saturation gas zones. In contrast, high compressional attenuation zones in the sonic frequency range (10-20 kHz) are affected by the presence of methane hydrates in the same well locations. Thus this study demonstrated the frequency dependence of attenuation in MH-bearing sediments; MH-bearing sediments cause attenuation in the sonic frequency range rather than the seismic frequency range.

Estimation of ultrasonic scattering attenuation in partially frozen brines using magnetic resonance images

Seismic attenuation is not due entirely to intrinsic properties; a component due to scattering effects is included. Although different techniques have been used to experimentally investigate the attenuation of seismic waves, not so many laboratory measurements of attenuation have taken into account the effect of scattering attenuation. Herein, partially frozen brine as a solid-liquid coexistence system is used to investigate attenuation phenomena. We obtained a series of 2D apparent diffusion coefficient (ADC) maps of the ice-brine coexisting system using a diffusion-weighted magnetic resonance imaging (DW-MRI) technique at −5°C , and found a strongly heterogeneous spatial distribution of unfrozen brine. From these maps, we constructed a synthetic seismic data set propagating through 2D media, and generated synthetic data with a second-order finite-difference scheme for the 2D acoustic wave equation. We estimated ultrasonic scattering attenuation in such systems by the centroid frequency shift method and ...

Laboratory experiments on compressional ultrasonic wave attenuation in partially frozen brines

Often, the loss mechanisms responsible for seismic attenuation are unclear and controversial. We used partially frozen brine as a solid-liquid coexistence system to investigate attenuation phenomena. Ultrasonic wave-transmission measurements on an ice-brine coexisting system were conducted to examine the influence of unfrozen brine in the pore microstructure on ultrasonic waves. We observed the variations of a 150–1000 kHz wave transmitted through a liquid system to a solid-liquid coexistence system, changing its temperature from 20°C to – 15°C . We quantitatively estimated attenuation in a frequency range of 350–600 kHz by considering different distances between the source and receiver transducers. We also estimated the total amount of frozen brine at each temperature by using the pulsed nuclear magnetic resonance (NMR) technique and related those results to attenuation results. The waveform analyses indicate that ultrasonic attenuation in an ice-brine coexisting system reaches its peak at −3°C , at whic...

Genetic, Epidemiologic and Clinicopathologic Studies of Japanese Asian Patients with Birt‐Hogg‐Dubé Syndrome

Birt–Hogg–Dubé syndrome (BHD) is a rare genetic disorder characterized by fibrofolliculomas, pulmonary cysts and renal cell carcinomas (RCCs). The affected individuals inherit germline mutations in the folliculin gene (FLCN). We investigated the mutation spectrum and clinicopathologic findings of 312 patients from 120 different families (119 Japanese and 1 Taiwanese). A total of 31 different FLCN sequence variants were identified. The majority were c.1285dupC (n = 34), c.1533_1536delGATG (n = 25), and c.1347_1353dupCCACCCT (n = 19). Almost all patients presented with pulmonary cysts. The incidence of RCCs in FLCN mutation carriers over the age of 40 was 34.8% (40/115). Fifty‐five RCC lesions were surgically resected; most were either chromophobe RCC (n = 24; 43.6%) or hybrid oncocytic/chromophobe tumors (19; 34.5%). Seventy‐six of 156 FLCN mutation carriers (120 probands and 36 sibs, 48.7%) had skin papules; however, cutaneous manifestations were so subtle that only one patient voluntarily consulted dermatologists. Japanese Asian BHD families have three FLCN mutational hotspots. Recurrent episodes of pneumothoraces are the major symptoms suggestive of a BHD diagnosis in our cohort. Characteristic features of lung and kidney lesions may be more informative than fibrofolliculomas as diagnostic criteria for BHD in the Japanese Asian population.

Magnetic spectral analysis in Portugal and its adjacent seas

Abstract Magnetic spectral analysis, which has often been applied to estimate Curie point depths, was used to delineate thermal and crustal structures of Portugal and its adjacent seas. The magnetic data set was the grid file of 5 km interval. Assuming random samplings from magnetic prisms, we obtained power spectra of two-dimensional square areas by the double Fourier transform and estimated statistical average depths. The cell-size for the area we used is 320 km. The average centroid depth, z 0 , was obtained automatically from the gradient of natural log of [(power spectrum)/(radial frequency)] in the range between 0.005 and 0.02 km −1 in frequency (50–200 km in wavelength). The average depth to the top of the magnetic layer, z t , was estimated from the gradient of the power spectrum between 0.02 and 0.04 km −1 in frequency (25–50 km in wavelength). The average depth to the bottom of the magnetic layer is calculated from 2 z 0 − z t . The results show that the bottom depths of land areas range between 20 and 55 km below sea level. The statistical errors of centroid depth are within 8 km. Marine linear magnetic anomalies widely cover the offshore areas, where random samples of prisms is inconsistent. We take one-dimensional analysis for the areas. The south of Portugal marks shallow depths of 20–30 km, while deep depth areas greater than 30 km spread widely in the north. One-dimensional analysis of the offshore area indicates the depth of marine magnetic layer of oceanic crust. The wide variation of depth is interpreted to be a reflection of the crustal and the thermal structures. Since the Moho must correspond to the base of the magnetic layer, the results could be the depths to the Moho instead of the Curie point isotherm in the northern Portugal. South Portuguese Zone is in the area ranging from 20 to 30 km in depth. These depths are shallower than the Moho. Two-dimensional forward modeling confirms that there is a throw of the bottom of the magnetic layer across the Ficalho over thrust from 35 to 40 km in the Ossa Morena Zone to 20–30 km in the South Portuguese Zone. There is a geothermal anomaly of high heat flow density values more than three times the normal average value. The Curie point isotherm estimated by the anomaly is shallower than the depth to the bottom of the magnetic layer. One interpretation is that the bottom of the magnetic layer corresponds to a Moho depth that could be 28–30 km in the Ossa Morena Zone and to a Curie point isotherm that could be 20–30 km in the South Portuguese Zone. The high heat flow density values of this area could be produced by hydrothermal convection along tectonic lines such as the Ferreira–Ficalho over thrust.

Seismic reflector imaging by prestack time migration in the Kakkonda geothermal field, Japan

We show that a prestack migration method improves the S/N ratio of seismic reflection profiling in the Kakkonda geothermal field where seismic reflection data are of poor quality. We use non-iterative prestack time migration (PSTM), which does not require multiple iterations to determine the velocity structure for prestack time migration. The optimum constant migration velocity can be determined at each image point from a migration velocity analysis based on primary diffraction patterns. Our results delineate a strong reflector beneath a zone of high seismicity. According to the correspondence between the fracture distribution, the distribution of microearthquakes, and geothermal structure, this reflector is interpreted to be a zone of low-angle fractures saturated with hydrothermal fluids, and to be strongly controlled by the geothermal structure.

Rheological implications of the strong seismic reflector in the Kakkonda geothermal field, Japan

Abstract We re-processed the seismic reflection survey data of the Kakkonda geothermal field. The pre-stack migration delineates a strong and continuous reflector between 1800- and 2800-m depth, below which formations are not reflective. Earthquake data exhibit seismicity in the upper crust. The lower boundary of seismogenic layer is interpreted as the brittle–ductile transition. The thermal structure is thought to be the major factor controlling its depth. We compared the strong reflector with the thermal and rheological structure from drillholes. The depth of the reflector corresponds to the top of the highly–very highly fractured zone observed from formation microscanner imagery (FMI) logging in the Miocene formations. The density of fracture in the Kakkonda granite is very low, suggesting that granite corresponds to the nonreflective zone. The temperature–depth profile of well WD-1a shows that the temperature at the highly–very highly fractured zone is about 350 °C. This corresponds to a hydrothermal convection zone filled with two-phase geothermal fluid. The cut-off depth of seismicity that indicates the brittle–ductile transition lies at the isotherm of 300–350 °C near the reflector. We conclude that the strong seismic reflector is a strong contrast in acoustic impedance at the top of the fractured layer. The fractured layer could be a decoupling plane caused by different tectonic behaviors between the upper brittle and the lower ductile layers or a dehydration front by thermal diffusion. The similarity between the strong reflector and K-horizon, the strong reflector, found in southern Tuscany, Italy suggests that the P-wave reflector at the top of highly fractured zone at the brittle–ductile transition be common in areas with magmatic activity.

Immunohistochemical characterization of renal tumors in patients with Birt-Hogg-Dubé syndrome.

Birt‐Hogg‐Dubé syndrome (BHD) is an autosomal dominant disorder associated with a germline mutation of folliculin (FLCN). The affected families are at a high risk for developing multiple renal cell carcinomas (RCC). Little is known about the immunostaining patterns of mutant FLCN‐associated RCCs. We investigated 32 RCCs obtained from 17 BHD patients. The studied tumors included chromophobe RCCs (n = 15), hybrid oncocytic/chromophobe tumors (HOCT) (n = 14) and clear cell RCCs (n = 3). Almost all chromophobe RCCs and HOCTs revealed positive staining for S100A1, Ksp‐cadherin and CD82. They stained either focally or diffusely for CK7, and were negative for CA‐IX. All clear cell RCCs were positively stained for CA‐IX and negative for CK7. These data confirmed that mutant FLCN‐associated oncocytic and clear cell RCCs exhibited generally similar immunostaining patterns compared to their sporadic counterparts. Frequent positive staining for S100A1, Ksp‐cadherin and CD82 in chromophobe RCCs and HOCTs indicated that these two types were relatively similar rather than distinctively different in their patterns of immunoreactivity. Characteristic peri‐nuclear halos and polygonal cells with clear cytoplasm, which often misleads pathologists into the diagnosis of clear cell RCC, should be carefully examined using an immunohistochemical panel including CA‐IX, Ksp‐cadherin, CD82 and CK7.

Association of inflammatory biomarkers with depressive symptoms and cognitive decline in a community-dwelling healthy older sample: A 3-year follow-up study

BACKGROUND The relationship between the pathophysiology of dementia and neuroinflammation is well-known. The number of reports stating that depression is a risk factor for dementia has recently been increasing. These epidemiological findings suggest the possibility that both depression and dementia have common pathophysiological backgrounds of neuroinflammation. METHODS The sample consists of 64 non-demented community-dwelling older participants aged 65 years or over. Participants were assessed at baseline (2004-2006) and 3 years later (2007-2009). Plasma concentration of markers of inflammation (interleukins (IL)-1β, IL-2, IL-6, soluble interleukin-2 receptor (sIL-2R), soluble interleukin-6 receptor (sIL-6R), high sensitivity C-reactive protein (hsCRP) and tumor necrosis factor (TNF)-α) were measured at baseline. Depression symptoms were assessed with the Beck Depression Inventory (BDI) and cognitive decline was assessed with the Mini-Mental State Examination (MMSE), Frontal Assessment Battery (FAB) and Clock Drawing Test (CDT) at baseline and follow-up. All analyses were adjusted for age, gender and years of education. RESULTS In the cross-sectional analysis, the present study found soluble IL-2 receptor (sIL-2R) to be associated only with the MMSE score at baseline in men. In the longitudinal analysis, none of our inflammatory biomarkers were associated with either depressive symptoms or cognitive decline. LIMITATIONS The present study consists of small number of participants and body mass index (BMI) scores were not obtained. CONCLUSIONS Our findings suggest that sIL-2R is associated with current cognitive function in men. None of our inflammatory markers predicted future depressive state or cognitive decline in our community-dwelling healthy older sample.

Seismic attenuation from VSP data in methane hydrate-bearing sediments

Recent seismic surveys have shown that the presence of methane hydrate (MH) in sediments has significant influence on seismic attenuation. I have used vertical seismic profile (VSP) data from a Nankai Trough exploratory well, offshore Tokai in central Japan, to estimate compressional attenuation in MH-bearing sediments at seismic frequencies of 30–110 Hz. The use of two different measurement methods (spectral ratio and centroid frequency shift methods) provides an opportunity to validate the attenuation measurements. The sensitivity of attenuation analyses to different depth intervals, borehole irregularities, and different frequency ranges was also examined to validate the stability of attenuation estimation. I found no significant compressional attenuation in MH-bearing sediments at seismic frequencies. Macroscopically, the peaks of highest attenuation in the seismic frequency range correspond to low-saturation gas zones. In contrast, high compressional attenuation zones in the sonic frequency range (10–20 kHz) are associated with the presence of methane hydrates at the same well locations. Thus, this study demonstrated the frequency-dependence of attenuation in MH-bearing sediments; MH-bearing sediments cause attenuation in the sonic frequency range rather than the seismic frequency range. As a possible reason why seismic frequencies in the 30–110 Hz range were not affected in MH-bearing sediments, I point out the effect of thin layering of MH-bearing zones.