Reconstruction of earthquake hazard in regions of sparse seismic monitoring

Studying strong motion records and the spatial distribution of ground shaking is of great importance in understanding the underlying causes of damage in earthquakes. Many regions in the world are either not instrumented or are sparsely instrumented. As such, significant opportunities for motion-damage correlations are lost. Two recent and damaging earthquakes belong to the class of lost opportunities, namely the Kashmir (Pakistan) earthquake of October 2005 and the Yogyakarta (Indonesia) earthquake of May 2006. In this paper, an overview of the importance of supply and demand studies in earthquake-stricken regions is given, followed by two examples of investigative engineering seismology aimed at reconstructing the hazard from sparse data. The paper closes with a plea for responsible authorities to invest in seismic monitoring networks in the very near future.     

Model-data fusion for seismic performance evaluation of an instrumented highway bridge

The paper presents a computationally efficient algorithm to integrate a probabilistic, non-Gaussian parameter estimation approach for nonlinear finite element models with the performance-based earthquake engineering (PBEE) framework for accurate performance evaluations of instrumented civil infrastructures. The algorithm first utilizes a minimum variance framework to fuse predictions from a numerical model of a civil infrastructure with its measured behavior during a past earthquake to update the parameters of the numerical model that is, then, used for performance prediction of the civil infrastructure during future earthquakes. A nonproduct quadrature rule, based on the conjugate unscented transformation, forms an enabling tool to drive the computationally efficient model prediction, model-data fusion, and performance evaluation. The algorithm is illustrated and validated on Meloland Road overpass, a heavily instrumented highway bridge in El Centro, CA, which experienced three moderate earthquake events in the past. The benefits of integrating measurement data into the PBEE framework are highlighted by comparing damage fragilities of and annual probabilities of damages to the bridge estimated using the presented algorithm with that estimated using the conventional PBEE approach.     

Linking the explicit probability of entrainment of instrumented particles to flow hydrodynamics

Obtaining a better understanding of the underlying dynamics of the interaction of turbulent flows and the bed surface that contains them, leading to the transport of coarse particles in fluvial, coastal, and aeolian environments, is considered as one of the fundamental objectives and the most complex problems in Earth surface dynamics and engineering. Recent technological advancements have made it possible to directly assess sediment entrainment rather than monitoring surrogate flow metrics, which could be related indirectly to sediment entrainment. In this work, a novel and low-cost instrumented particle, 7 cm in diameter, is used to directly assess the incipient entrainment of a coarse particle resting on a bed surface. The particle has inertial measurement units (IMUs) embedded within its waterproof shell, enabling it to track the particle's motions and quantify its inertial dynamics. The sensors of the instrumented particle are calibrated using simple and easy-to-validate theoretically physical motions to estimate the uncertainties in their readings, which are reduced using an inertial sensor fusion process. A series of well-designed laboratory flume incipient motion experiments are performed to assess the entrainment of the instrumented particle for a range of flowrates near the threshold of motion. The readings of the instrumented particle are used to derive metrics that are related to the probability of its incipient entrainment. The flow velocity measurements are obtained for the experiment runs, and the derived metrics are explicitly linked to the flow hydrodynamics responsible for the entrainment. The framework presented in this work can be used for a range of similar applications of low-cost instrumented particles, spanning the interface of sensing and instrumentation in engineering (i.e., infrastructure and environmental monitoring) and geosciences (e.g., habitat assessment).     

Nonlinear FE model updating and reconstruction of the response of an instrumented seismic isolated bridge to the 2010 Maule Chile earthquake

Nonlinear finite element (FE) modeling has been widely used to investigate the effects of seismic isolation on the response of bridges to earthquakes. However, most FE models of seismic isolated bridges (SIB) have used seismic isolator models calibrated from component test data, while the prediction accuracy of nonlinear FE models of SIB is rarely addressed by using data recorded from instrumented bridges. In this paper, the accuracy of a state‐of‐the‐art FE model is studied through nonlinear FE model updating (FEMU) of an existing instrumented SIB, the Marga‐Marga Bridge located in Viña del Mar, Chile. The seismic isolator models are updated in 2 phases: component‐wise and system‐wise FEMU. The isolator model parameters obtained from 23 isolator component tests show large scatter, and poor goodness of fit of the FE‐predicted bridge response to the 2010 Mw 8.8 Maule, Chile Earthquake is obtained when most of those parameter sets are used for the isolator elements of the bridge model. In contrast, good agreement is obtained between the FE‐predicted and measured bridge response when the isolator model parameters are calibrated using the bridge response data recorded during the mega‐earthquake. Nonlinear FEMU is conducted by solving single‐ and multiobjective optimization problems using high‐throughput cloud computing. The updated FE model is then used to reconstruct response quantities not recorded during the earthquake, gaining more insight into the effects of seismic isolation on the response of the bridge during the strong earthquake.     

基于风云二号X射线监测数据的短波通讯可用频率预报

介绍了风云二号气象卫星空间环境探测资料的处理、显示技术。研究了如何利用风云二号X射线探测数据计算短波通讯最低可用频率及电离层D层的电波吸收,并设计了一个基于风云二号X射线探测数据的短波通讯最低可用频率经验预报模式。     

一幢钢筋混凝土建筑结构的强地震反应观测

介绍了美国加州强震观测计划（CSMIP）中一幢建筑结构地震反应台阵的观测方案，描述了被观测结构的有关情况，给出了该台阵于1994年美国北岭地震中获得的结构地震反应的观测资料。     

Modelling the water balance in the glacierized Parón Lake basin (White Cordillera,Peru) / Modélisation du bilan hydrique du bassin versant englacé du Lac Parón (Cordillère Blanche,Pérou)

Abstract

The White Cordillera (northern Peru), with a glacial surface of 631 km², is the largest glacierized mountain range in the Tropics. Due to the lack of physical data from most of its sub-basins, it is difficult to build a physical model to estimate the water resource flowing from the glaciers at the present time and a fortiori for the future. The most recent GCM simulations indicate a significant increase in the temperature and an accelerated shrinking of the glaciers. Consequently, we sought a model that would be based on the data available within instrumented sub-basins. A theoretical/conceptual water model makes it possible to quantify the local glacier contribution, which could then be applied to the other non-instrumented sub-basins. A total of 43.6% of Parón Lake's instrumented sub-basin area (47.4 km²) corresponds to glacial surfaces. Within this sub-basin, a smaller watershed (8.8 km²), called Artesón, with 72.9% glacierized area, has been accurately observed over a 5-year hydrological period (September 2000–August 2005). This information allowed us to calibrate the model over the Artesón sub-basin. The parameters obtained were applied to the entire Parón basin using the same modelling approach.     

Experimental study of seismic behavior of two hilly sites in Tehran and comparison with 2D and 3D numerical modeling

Two hilly sites were selected to study seismic site response due to topography effects. The sites were selected in a manner to be as much as possible homogenous and free of the soft soil layers effects. The hills were instrumented by nine velocimetric stations to record microtremors and the obtained data were analyzed using horizontal to vertical spectral ratios. Some standard spectral ratio tests were performed on noise as well. Then the instrumented hills were modeled (both 2D and 3D) assuming a linear elastic constitutive behavior subjected to vertically propagating SV and P Ricker wavelets. All calculations were performed in time domain using direct boundary element method. Different transfer function components, amplification patterns and spectral ratios were calculated in frequency domain. The frequency of vibration, obtained by experimental studies, is between 4 and 5 Hz for both of the hills. The spectral ratios derived by numerical simulations were compared with the observed spectral ratios. They show relatively good similarities between the results of these two methods. The frequencies of vibration derived from different methods seem to be nearly identical. The agreement in term of resonance frequency between microtremors and numerical modeling suggests that noise measurements could represent a simple, even if preliminary, tool in order to identify possible topographic amplification.     

A data‐based mechanistic modelling (DBM) approach to understanding dynamic sediment transmission through Wyresdale Park Reservoir,Lancashire, UK

This paper outlines the application of a new data‐based mechanistic (DBM) modelling methodology to the characterization of the sediment transmission dynamics in a small upland reservoir, Wyresdale Park, Lancashire. The DBM modelling strategy exploits advanced statistical procedures to infer the dynamic model structure and its associated parameters directly from the instrumented data, producing a parametrically efficient, continuous time, transfer function model which relates suspended sediment load at the reservoir inflow to the outflow at the event scale. The associated differential equation model parameters have physical attributes which can be interpreted in terms of sediment transmission processes and associated reservoir trap efficiency. Sedigraph analysis suggests that wind‐induced resuspension episodically supplies an additional load to the reservoir outlet. The stochastic nature of the DBM model makes it ideal for evaluating the effects of uncertainty through Monte Carlo simulations (MCS) for discharge and sediment transmission. Copyright © 2000 John Wiley & Sons, Ltd.     

Assessing sediment transport dynamics from energy perspective by using the instrumented particle

Sediment transport has been extensively studied. There is still a need to learn more about the mechanisms that make bed particles move, which is caused by turbulent flow in the low transport stages(above the motion threshold and below continuous transport). This work is focused on the use of an advanced tool to obtain a better perception of sediment transport dynamical methods: an instrumented particle equipped with a micro-electromechanical systems(MEMS) sensor. Particle transport experiments w...     

Evaluation of the natural vibration frequencies of a historical masonry building accounting for SSI

The dynamic identification of a historical masonry palace located in Benevento (Italy) has been carried out. The case study is representative of many buildings located in historic Italian centres. Since the building has been instrumented by the Department of Civil Protection with a permanent dynamic monitoring system, some of the recorded data, acquired in various operating conditions have been analysed with basic instruments of the Operational Modal Analysis in order to identify the main eingenfrequencies and vibration modes of the structure. The experimental results have been compared to the numerical outcomes provided by a detailed three-dimensional Finite Element (FE) model of the building where Soil–Structure Interaction (SSI) has been taken into account. The comparison of experimental vs. numerical frequencies and vibration modes of the palace evidenced the role exerted by the subsoil on the dynamic response of the building.     

Influence of Pressure Change During Hydraulic Tests on Fracture Aperture

In a series of field experiments, we evaluate the influence of a small water pressure change on fracture aperture during a hydraulic test. An experimental borehole is instrumented at the Korea Atomic Energy Research Institute (KAERI) Underground Research Tunnel (KURT). The target fracture for testing was found from the analyses of borehole logging and hydraulic tests. A double packer system was developed and installed in the test borehole to directly observe the aperture change due to water pressure change. Using this packer system, both aperture and flow rate are directly observed under various water pressures. Results indicate a slight change in fracture hydraulic head leads to an observable change in aperture. This suggests that aperture change should be considered when analyzing hydraulic test data from a sparsely fractured rock aquifer.     

Lateral moisture flow beneath a sandy hillslope without an apparent impeding layer

Part of a small drainage basin on the Sevilleta National Wildlife Refuge (about 25 km north of Socorro, NM) was intensively instrumented with soil monitoring equipment to estimate natural ground-water recharge. Soil-moisture data were analysed with special attention to characterizing the influence of topography on the direction of vadose water flow paths in fine to medium aeolian sand. Moisture content data were obtained by the neutron scattering technique, and hydraulic head data were obtained using tensiometers. In addition, tracer experiments were conducted on a sandy hillslope to delineate the flow paths of vadose water. The results indicate that there is a strong lateral component to unsaturated flow on a hillslope, even in the absence of apparent sublayers of much lower permeability. Darcian calculations estimate the long-term, steady, deep flux beneath a concave location to be about 4 per cent of an assumed mean annual precipitation of 20 cm. The deep soil water flux downward varied by several orders of magnitude during the 17 month period of record.     

Evaluation model of landslide hazards induced by the 2008 Wenchuan earthquake using strong motion data

Landslides induced by the 2008 Wenchuan earthquake in the Longmenshan area were relatively well instrumented,which makes it possible to investigate the landslides using ground motion records.Firstly,this paper analyzes the data from Wenchuan earthquake on both regional and local site scale.The analyses show that the Newmark accumulative displacement calculated from the ground motion recorded in a particular geological hazard zone corresponds to the hazard intensity in that zone;the larger the displacemen...     

Lessons learned and need for instrumented liquefaction sites

Instrumented sites provide essential information for understanding and modeling of ground response and ground deformation. For example, significant new lessons were learned from responses at the Wildlife Liquefaction Array (WLA) including: (1) soil softening led to lengthening of period of transmitted ground motions; (2) soil softening also led to attenuation of short-period spectral accelerations (<0.7 s); (3) amplification of long period motions (>0.7 s) occurred due to liquefaction-induced ground oscillation; and (4) ground oscillation led to a continued rise of pore water pressures after strong ground shaking ceased. A new and expanded instrumented site is being developed 70 m downstream from the old WLA site as part of the NSF Network for Earthquake Engineering Simulation (NEES). The new site has more accelerometers, piezometers and ground deformation measurement devices and the data will be streamed to the NEES-grid in near real time.     

Hydrological data assimilation with the Ensemble Square-Root-Filter: Use of streamflow observations to update model states for real-time flash flood forecasting

The objective of the study is to evaluate the potential of a data assimilation system for real-time flash flood forecasting over small watersheds by updating model states. To this end, the Ensemble Square-Root-Filter (EnSRF) based on the Ensemble Kalman Filter (EnKF) technique was coupled to a widely used conceptual rainfall-runoff model called HyMOD. Two small watersheds susceptible to flash flooding from America and China were selected in this study. The modeling and observational errors were considered in the framework of data assimilation, followed by an ensemble size sensitivity experiment. Once the appropriate model error and ensemble size was determined, a simulation study focused on the performance of a data assimilation system, based on the correlation between streamflow observation and model states, was conducted. The EnSRF method was implemented within HyMOD and results for flash flood forecasting were analyzed, where the calibrated streamflow simulation without state updating was treated as the benchmark or nature run. Results for twenty-four flash-flood events in total from the two watersheds indicated that the data assimilation approach effectively improved the predictions of peak flows and the hydrographs in general. This study demonstrated the benefit and efficiency of implementing data assimilation into a hydrological model to improve flash flood forecasting over small, instrumented basins with potential application to real-time alert systems.     

3D Response analysis of an instrumented hill at Matsuzaki, Japan, by a spectral method

Strong ground motion observed at an instrumented hill site is first analysed through the standard (SSR) and the horizontal-to-vertical (HVSR) spectral ratio techniques. A reasonable agreement is found between these approaches. The observations are then compared with 3D numerical simulations, performed with a highly efficient numerical code based on a spectral method, that allowed for reasonable computer times also on a PC. The observed amplification is significantly higher than that computed with a 3D homogeneous model of the mountain, suggesting that local response is governed by large-scale and small-scale soil heterogeneities rather than by topographic site effects. The introduction of a local near-surface inclusion of nonhomogeneous soil material under one of the recording stations has not significantly improved the numerical results. The observed data are also compared with the results of simplified simulations, either using 2D homogeneous models or coupling the 3D response with a 1D local soil profile. The results of such simplified approaches are discussed and their usefulness is emphasised.     

Plasma density over Svalbard during the ISBJØRN campaign

In 1997, reliable operation of the EISCAT Svalbard Radar (ESR) was achieved and a rocket launching facility at Ny Ålesund on Svalbard (79°N, 12°E) (SVALRAK) was established. On 20 November, 1977, the first instrumented payload was launched from SVALRAK. Although the payload configuration had been flown many times previously from Andøya Rocket Range on the Norwegian mainland, this presented an unprecedented in situ determination of positive ion density over Svalbard. Simultaneously, ESR measured similar density profiles but in a higher altitude regime. We have combined the ESR measurements with ionosonde data to establish a calibration and subsequently combined the ground-based and in situ determined profiles to give a composite positive ion density profile from the mesosphere to the thermosphere.     

Torsion in two buildings—1987 whittier narrows earthquake

Study of the data from the extensively instrumented buildings in the 1987 Whittier Narrows earthquake suggests that torsional modes probably were excited in buildings that outwardly appear quite symmetric. Accordingly this study involves: (i) investigation of the observed response of two low-rise buildings in both the elastic and moderately inelastic domains, (ii) comparison of such behaviour with the results obtained from modelling studies, and (iii) examination of the possible effects arising from stronger shaking. The study was directed towards attempting to provide a partial answer to the critical question of whether or not the torsional response was important in the gross total response of these low-rise buildings, and to what extent torsional concepts should be considered in design. Also the numerical results were extrapolated to examine the survivability of the same buildings if subjected to a somewhat stronger earthquake. The ultimate goal was to contribute insight to the practical guidelines for design and analysis of low-rise buildings subjected to strong ground motion.     

A decision-theory methodology for the selection of buildings for strong-motion instrumentation

Current projections indicate that six buildings per year will continue to be instrumented under the California Strong-Motion Instrumentation Program for the next several decades. In order to select these buildings systematically for instrumentation, we have developed a methodology that incorporates the fundamental elements of decision theory. These elements include an identification of the types of buildings that should be instrumented, a definition of the expected severity of ground shaking at each possible building site along with the probability of occurrence, and a quantification of the relative value of obtaining a building-response record for each building type. Using this information, we can apply decision theory to calculate the expected utility (degree of preference) of instrumenting buildings of a particular type at various sites. The sites are then ranked in order of preference for each building type. This procedure, developed for the California Strong-Motion Instrumentation Program, can be extended to instrumentation programs in other areas.