Modelling landslide debris flow with entrainment: development and validation

The volume and mobility of a debris flow could increase with distance travelled as it has the potential to entrain a substantial amount of channel-bed material along its travel path. This entrainment effect renders the debris flow more devastating to downslope populations and facilities. Over the past two decades, the Geotechnical Engineering Office (GEO) of Hong Kong has expended considerable effort to develop debris mobility modelling tools for use in routine engineering practice for forward prediction purposes. Recently, GEO has completed a study to enhance an in-house debris mobility code. Physical parameters which can be estimated from the field by engineers or geologists are incorporated in the code to predict entrainment effects in a simple and rational manner. This allows the modelling of varying entrainment potential along a debris flow path. The code has been checked against simplified analytical solutions and validated against field observations in a major historical landslide event involving highmobility debris flows in Hong Kong. The numerical modelling results indicated that simulated entrainment volume and mobility characteristics are broadly consistent with geological field mapping records

Shear-Wave Velocity Characterization of the USGS Hawaiian Strong-Motion Network on the Island of Hawaii and Development of an NEHRP Site-Class Map

To assess the level and nature of ground shaking in Hawaii for the purposes of earthquake hazard mitigation and seismic design, empirical ground-motion prediction models are desired. To develop such empirical relationships, knowledge of the subsurface site conditions beneath strong-motion stations is critical. Thus, as a first step to develop ground-motion prediction models for Hawaii, wspectral-analysis-of-surface-waves (SASW) profiling was performed at the 22 free-field U.S. Geological Survey (USGS) strong-motion sites on the Big Island to obtain shear-wave velocity (V(S)) data. Nineteen of these stations recorded the 2006 Kiholo Bay moment magnitude (M) 6.7 earthquake, and 17 stations recorded the triggered M 6.0 Mahukona earthquake. V(S) profiling was performed to reach depths of more than 100 ft. Most of the USGS stations are situated on sites underlain by basalt, based on surficial geologic maps. However, the sites have varying degrees of weathering and soil development. The remaining strong-motion stations are located on alluvium or volcanic ash. V(S30) (average V(S) in the top 30 m) values for the stations on basalt ranged from 906 to 1908 ft/s [National Earthquake Hazards Reduction Program (NEHRP) site classes C and D], because most sites were covered with soil of variable thickness. Based on these data, an NEHRP site-class map was developed for the Big Island. These new V(S) data will be a significant input into an update of the USGS statewide hazard maps and to the operation of ShakeMap on the island of Hawaii.George E. Brown, Jr. Network for Earthquake Engineering Simulation (NEES) under NSF CMS-0086605FEMA HSFEHQ-06-D-0162, HSFEHQ-04-D-0733U.S. Geological Survey, Department of the Interior 08HQGR0036Geotechnical Engineering Cente

Low potential for large intraslab earthquakes in the central Cascadia Subduction Zone

Abstract The Cascadia subduction zone (CSZ) can be divided into three distinct sections based on the characteristics of intraslab seismicity. Based on a 150-year historical record, no moderate-to-large intraslab earthquakes of moment magnitude (M) 5.5 or greater have occurred within the subducting Juan de Fuca plate of the central CSZ from south of the Puget Sound in northwestern Washington to the Oregon-California border. Also very few intraslab earthquakes as small as M 3 have been instrumentally located within the central CSZ since 1960, and a Wadati-Benioff zone is not apparent. In the southern CSZ beneath northwestern California, a WadatiBenioff zone is present to a depth of about 40 km, but no large Gorda block earthquakes have been observed in the downgoing slab, although large events have occurred near the trench axis. In contrast, the Puget Sound region within the northern CSZ has been repeatedly shaken by large intraslab earthquakes of M Ն6.5 in the depth range of 40 to 60 km, such as the recent 2001 M 6.8 Nisqually event. A critical question addressed in this article is what is the potential for such large, shallow intraslab earthquakes in the central CSZ beneath western Oregon and southwestern Washington? I have evaluated the available information on the thermal and physical properties, geometry, and historical and contemporary seismicity of the central CSZ, and performed thermal modeling. Based on these analyses and comparisons with other subduction zones worldwide, the lack of shallow intraslab earthquakes in the central CSZ is not unusual. The hot temperatures (Ͼ500ЊC) within the Juan de Fuca plate, particularly below a depth of 40 km where large events are expected, are not conducive to earthquake generation, resulting in either the complete absence of M Ն6.5 shallow intraslab earthquakes or long recurrence intervals (hundreds of years) between such events. Temperatures appear to be sufficiently high in the central CSZ so that no Wadati-Benioff zone can exist even at shallow depths (Ͻ40 km). The young plate age, slower convergence rate, and the insulating effect of the Siletz terrane above the plate are factors that probably lead to the hot temperatures in this portion of the slab. The variability in the maximum depth of the Wadati-Benioff zone along the CSZ, 60 km beneath the Puget Sound, 40 km within the subducting Gorda block, and essentially zero in the central CSZ, reflect the differing temperature conditions, that is, the cutoff temperature varies with depth and rock composition, and also the potential for large shallow intraslab earthquakes. In addition to the effects of temperature, the level of tectonic stresses, which vary along the length of the CSZ, must also be a factor in controlling the occurrence of large intraslab earthquakes. Large events can occur in the Puget Sound region, probably because of cooler intraslab temperatures and possibly because of a stress concentration or zone of weakness along the pronounced arch in the Juan de Fuca plate. A previous study has suggested an intraslab subduction zone origin for a M 7.3 earthquake that occurred in 1873 near the town of Brookings, in southernmost Oregon. However, analysis of its seismotectonic setting and comparison with other historical earthquakes in northernmost California suggest that the event probably had a very shallow origin within the Gorda block (southern CSZ) and was not a deep intraslab earthquake in the central CSZ

Peptides as potent antimicrobials tethered to a solid surface: Implications for medical devices

Medical devices are an integral part of therapeutic management; despite their importance, they carry a significant risk of microbial infection. Bacterial attachment to a medical device is established by a single, multiplying organism, leading to subsequent biofilm formation. To date, no preventative measures have impacted the incidence of device-related infection. We report the bidirectional covalent coupling of an engineered cationic antimicrobial peptide (eCAP), WLBU2, to various biological surfaces is accomplished. These surfaces included (i) a carbohydrate-based gel matrix, (ii) a complex polymeric plastic bead, and (iii) a silica-calcium phosphate nanocomposite associated with bone reconstruction. WLBU2-conjugated surfaces are shown to retain potent antimicrobial activity related to bacterial surface adhesion. This study provides proof of principle that covalently coating laboratory and bone-regenerating materials with eCAPs has the potential for decreasing infection rates of implanted devices. These findings have important consequences to the patient management component of our current health care technology

Objective Assessment and Design Improvement of a Staring, Sparse Transducer Array by the Spatial Crosstalk Matrix for 3D Photoacoustic Tomography.

Accurate reconstruction of 3D photoacoustic (PA) images requires detection of photoacoustic signals from many angles. Several groups have adopted staring ultrasound arrays, but assessment of array performance has been limited. We previously reported on a method to calibrate a 3D PA tomography (PAT) staring array system and analyze system performance using singular value decomposition (SVD). The developed SVD metric, however, was impractical for large system matrices, which are typical of 3D PAT problems. The present study consisted of two main objectives. The first objective aimed to introduce the crosstalk matrix concept to the field of PAT for system design. Figures-of-merit utilized in this study were root mean square error, peak signal-to-noise ratio, mean absolute error, and a three dimensional structural similarity index, which were derived between the normalized spatial crosstalk matrix and the identity matrix. The applicability of this approach for 3D PAT was validated by observing the response of the figures-of-merit in relation to well-understood PAT sampling characteristics (i.e. spatial and temporal sampling rate). The second objective aimed to utilize the figures-of-merit to characterize and improve the performance of a near-spherical staring array design. Transducer arrangement, array radius, and array angular coverage were the design parameters examined. We observed that the performance of a 129-element staring transducer array for 3D PAT could be improved by selection of optimal values of the design parameters. The results suggested that this formulation could be used to objectively characterize 3D PAT system performance and would enable the development of efficient strategies for system design optimization

Dekomposisi dan Rekombinasi Pengacakan Citra Digital dengan Logistic Mapping

Beberapa citra digital membutuhkan privasi dan kerahasiaan, seperti citra medis, citra diagnosa medis jarak jauh, citra rahasia melalui komunikasi internet, atau citra rahasia kemiliteran. Salah satu cara untuk mengamankan informasi di dalam citra digital adalah dengan melakukan pengacakan (scrambling). Penelitian ini mengacak nilai piksel citra digital dengan mengubah nilai piksel dari sistem bilangan desimal menjadi bilangan basis empat (kuartener), kemudian mengurai (dekomposisi) keempat bit kuartener dan melakukan pengacakan terhadap keempat posisi bit berdasarkan pada bilangan acak yang dihasilkan oleh algoritma logistic mapping, kemudian bit hasil pengacakan digabungkan kembali (rekombinasi) untuk menghasilkan nilai piksel baru. Logistic mapping merupakan penghasil bilangan acak yang mampu menghasilkan deretan bilangan yang acak berdasarkan nilai kunci µ (3.569945 < µ < 4) dan nilai awal x0 (0 < x0 < 1). Hasil penelitian ini dapat melakukan pengacakan terhadap citra digital dengan dekomposisi dan rekombinasi nilai piksel berdasarkan pada nilai acak yang dihasilkan oleh algoritma logistic mapping. Hasil pengujian menunjukkan bahwa pasangan kunci-1 (µ1, x1) memiliki sensitivitas paling tinggi dalam mengacak citra, kemudian diikuti oleh pasangan kunci-2 (µ2, x2), pasangan kunci-3 (µ3, x3) dan pasangan kunci-4 (µ4, x4)

Seismic Hazard Evaluation for Design of San Vicente Dam Raise

The San Diego County Water Authority (Water Authority) is undertaking a raise of the existing San Vicente Dam to provide both emergency and carryover storage to increase local reservoir supplies in San Diego County, California, USA. The emergency storage is required in case of a disruption to the imported water transmission system from floods or earthquakes and the carry-over storage would be utilized to store water during “wet” seasons to carry-over to seasons of drought. The existing San Vicente Dam is a 220 foot (67 m) high concrete gravity dam completed in 1943 with 90,063 acre-feet of storage. The raised San Vicente Dam will be about 337 feet (102.3 m) high, creating an approximately 247,000 acre-foot reservoir. The dam raise will be constructed using the roller compacted concrete (RCC) method. This paper presents details of the seismic hazard evaluation that formed the basis for development of strong ground motions that were considered in final design of the dam raise. The dam is under the jurisdiction of the California Department of Water Resources, Division of Safety of Dams (DSOD) which requires the use of deterministic ground motions for design. However, the earthquake ground motions at the site are largely controlled by background (or random) earthquakes, which cannot be adequately addressed using deterministic methods alone. This prompted the development of supplemental seismic design ground motions based on a probabilistic seismic hazard analysis (PSHA). The PSHA was performed incorporating the latest information on seismic sources and recently developed Next Generation of Attenuation (NGA) relationships. Based on the results of the PSHA, ground motion parameters (response spectra and time histories) were developed for final design of the dam raise. Comparisons of the deterministic and probabilistic ground motions are provided. Application of the NGA relationships resulted in lower estimates of peak ground accelerations than what were obtained based on the previous attenuation relationships due to the use of the site-specific shear wave velocities of the foundation materials

Is Europe prepared to go digital? making the case for developing digital capacity: An exploratory analysis of Eurostat survey data

Digital divides are globally recognised as a wicked problem that threatens to become the new face of inequality. They are formed by discrepancies in Internet access, digital skills, and tangible outcomes (e.g. health, economic) between populations. Previous studies indicate that Europe has an average Internet access rate of 90%, yet rarely specify for different demographics and do not report on the presence of digital skills. This exploratory analysis used the 2019 community survey on ICT usage in households and by individuals from Eurostat, which is a sample of 147,531 households and 197,631 individuals aged 16-74. The cross-country comparative analysis includes EEA and Switzerland. Data were collected between January and August 2019 and analysed between April and May 2021. Large differences in Internet access were observed (75-98%), especially between North-Western (94-98%) and South-Eastern Europe (75-87%). Young populations, high education levels, employment, and living in an urban environment appear to positively influence the development of higher digital skills. The cross-country analysis exhibits a positive correlation between high capital stock and income/earnings, and the digital skills development while showing that the internet-access price bears marginal influence over digital literacy levels. The findings suggest Europe is currently unable to host a sustainable digital society without exacerbating cross-country inequalities due to substantial differences in internet access and digital literacy. Investment in building digital capacity in the general population should be the primary objective of European countries to ensure they can benefit optimally, equitably, and sustainably from the advancements of the Digital Era