Strong-motion Sensors Research Articles

Real-time coseismic wave retrieving by integrated Kalman filter with observations of GPS, Glonass and strong-motion sensor

A method of real-time coseismic wave retrieving was proposed based on the tight integration of GPS, Glonass and strong-motion sensor observations, the validation and precision analysis have been made by an experimental data. The series of results have been shown that: by the integrated Kalman filter and multi-sensors, the coseismic waves can be optimally recovered by complement the advantages of each other, especially when the observation conditions are very bad. In additional, the results are not significantly effected by different receiver clock error processes for the integration solution.

High-rate coseismic displacements from tightly integrated processing of raw GPS and accelerometer data

High-rate GPS and seismic sensors are mutually contributing to seismological applications for capturing earthquake-induced coseismic displacements. In this study, we propose an approach for tightly integrating GPS and strong motion data on raw observation level to increase the quality of the derived displacements. The performance of the proposed approach is demonstrated using 5 Hz high-rate GPS and 200 Hz strong motion data collected during the El Mayor–Cucapah earthquake (M w 7.2, 2010 April 4) in Baja California, Mexico. The new approach not only takes advantages of both GPS and strong motion sensors, but also improves the reliability of the displacement by enhancing GPS integer-cycle phase ambiguity resolution, which is very critical for deriving displacements with highest quality.

Recent Progress of Seismic Observation Networks in Japan

Before the occurrence of disastrous Kobe earthquake in 1995, the number of high sensitivity seismograph stations operated in Japan was nearly 550 and was concentrated in the Kanto and Tokai districts, central Japan. In the wake of the Kobe earthquake, Japanese government has newly established the Headquarters for Earthquake Research Promotion and started the reconstruction of seismic networks to evenly cover the whole Japan. The basic network is composed of three seismographs, i.e. high sensitivity seismograph (Hi-net), broadband seismograph (F-net), and strong motion seismograph (K-NET). A large majority of Hi-net stations are also equipped with a pair of strong motion sensors at the bottom of borehole and the ground surface (KiK-net). A plenty of high quality data obtained from these networks are circulated at once and is producing several new seismological findings as well as providing the basis for the Earthquake Early Warning system. In March 11, 2011, "Off the Pacific coast of Tohoku Earthquake" was generated with magnitude 9.0, which records the largest in the history of seismic observation in Japan. The greatest disaster on record was brought by huge tsunami with nearly 20 thousand killed or missing people. We are again noticed that seismic observation system is quite poor in the oceanic region compared to the richness of it in the inland region. In 2012, NIED has started the construction of ocean bottom seismic and tsunami observation network along the Japan Trench. It is planned to layout 154 stations with an average spacing of 30km, each of which is equipped with an accelerometer for seismic observation and a water pressure gauge for tsunami observation. We are expecting that more rapid and accurate warning of earthquake and tsunami becomes possible by this observing network.

Rapid Estimation of Earthquake Source and Ground-Motion Parameters for Earthquake Early Warning Using Data from a Single Three-Component Broadband or Strong-Motion Sensor

We propose a new algorithm to rapidly determine earthquake source and ground-motion parameters for earthquake early warning (EEW). This algorithm uses the acceleration, velocity, and displacement waveforms of a single three-component broadband (BB) or strong-motion (SM) sensor to perform real-time earthquake/noise discrimination and near/far source classification. When an earthquake is detected, the algorithm estimates the moment magnitude M, epicentral distance Δ, and peak ground velocity (PGV) at the site of observation. The algorithm was constructed by using an artificial neural network (ANN) approach. Our training and test datasets consist of 2431 three-component SM and BB records of 161 crustal earthquakes in California, Japan, and Taiwan with 3.1 ≤ M ≤ 7.6 at Δ ≤ 115 km. First estimates become available at t_0 = 0.25 s after the P pick and are regularly updated. We find that displacement and velocity waveforms are most relevant for the estimation of M and PGV, while acceleration is important for earthquake/noise discrimination. Including site corrections reduces the errors up to 10%. The estimates improve by an additional 10% if we use both the vertical and horizontal components of recorded ground motions. The uncertainties of the predicted parameters decrease with increasing time window length t_0; larger magnitude events show a slower decay of these uncertainties than small earthquakes. We compare our approach with the τ_c algorithm and find that our prediction errors are around 60% smaller. However, in general there is a limitation to the prediction accuracy an EEW system can provide if based on single-sensor observations.

Buildings Subjected to Recurring Earthquakes: A Tale of Three Cities

Three different buildings built according to the same design have experienced three different near-field strong ground motions over a period of 11 years in three different cities in Turkey. The input motion was known for each because strong-motion sensors were located adjacent or close to the buildings. We examine the performance of the five-story, reinforced concrete-frame buildings. Bidirectional nonlinear time history and nonlinear static analyses on 3-D analytical models are performed. The principal focus is to assess whether the analytical model of the buildings could indicate column-beam damage consistent with that observed at the sites after the earthquakes. Results illustrate that nonlinear time history analyses are capable of indicating the occurrence of shear failure in captive columns; however, they overestimate the global damage. The overestimation is greater where the building sustained a pulse-type motion without significant distress. It appears that difference between visual observations and analytical results persists.

The April 6, 2009, Mw 6.3, L'Aquila sequence: weak-motion and strong-motion data recorded by the RAIS temporary stations

The aim of this study is the sharing of waveforms recorded by several Istituto Nazionale di Geofisica e Vulcanologia (INGV) temporary stations (managed by the Milan-Pavia section; INGV MI-PV). These stations were installed after the April 6, 2009, Mw 6.3, L'Aquila earthquake (central Italy). The work synthesizes the activities conducted in the field by the INGV MI-PV working group over the three months following the mainshock. The field activities were developed in four different phases that were defined according to their time periods. Starting from April 7, 2009, for the first phase, the temporary stations were installed in correspondence with the more damaged areas. The scope was to record the strongest aftershocks in the days that followed the mainshock. In this phase, the stations were composed of a six-component acquisition system that was coupled with both a weak-motion and a strong-motion sensor. After the first month, the last three phases of installation investigated the seismic responses of sites located in the epicentral area, involving villages within a radius of about 20 km from the epicenter of the April 6 mainshock. In this way, over four specific time-period phases, the stations were installed in sites with different lithological and geomorphological conditions. The instruments worked from April 7 to July 14, 2009; in this period, 9,155 aftershocks (134,262 accelerometric waveforms and 133,242 velocimetric waveforms), with ML ≤5.3 were recorded. This study describes the dataset of these earthquake waveforms recorded with both velocity and acceleration transducers. Selected waveforms are available through ftp://ftp.mi.ingv.it/download/RAIS-TS_rel01/, with their corresponding information concerning instrumental characteristics, installation sites, and earthquakes recorded.

Demonstration of Earthquake Early Warning Using Total Displacement Waveforms from Real-time GPS Networks

Earthquake early warning (EEW) systems have historically been based on traditional seismic instrumentation to provide rapid location of the earthquake source and its magnitude. Seismic-based systems currently exist in Japan (Nakamura 1989; Kanamori 2007), Mexico (Espinosa-Aranda et al. 1995), Taiwan (Wu and Kanamori 2005a, 2005b), Turkey, and Romania (Wenzel et al. 1999; Ionescu et al. 2007), and are under development in California (Allen and Kanamori 2003). Instrumentation includes broadband velocity and strong motion acceleration sensors, which measure dynamic ground motions with great accuracy ( e.g. , Heaton 1985). Currently, seismic early warning of events requires continuous monitoring of a suite of stations looking for changes in key parameters. Most algorithms use displacement when trying to estimate the potential magnitude of an event from the initial few seconds. The magnitude estimates are made on the ratio of the short-term average displacement to the long-term average and on the apparent frequency of the initial energy. With seismic data, displacement has to be obtained by an integration of the broadband sensors or a double integration of the strong motion sensors. Due to the bandwidth and the dynamic range limits of seismometers, the accuracy of displacements so derived is poor. Seismic instruments are also affected by sensor tilts, long-term drifts, and DC offsets. These problems are not present in displacements measured by continuous GPS (CGPS) instruments. While the seismic measurements provide a powerful constraint on the much noisier GPS measurements, the GPS receiver, unlike the seismometer, measures displacement directly and never clips, making it particularly sensitive to large earthquakes, which are the main focus of EEW. CGPS instruments can be used to directly measure dynamic displacements (“GPS Seismology”— Nikolaidis et al. 2001; Larson et al. 2003) as well as static (coseismic) displacements (“Earthquake Geodesy”—Bock et al. 1993; Blewitt et …

Converting Strong-motion Networks to Arrays via Common Triggering

Small-aperture, strong-motion arrays are of great importance for earthquake engineering and engineering seismology. Their capabilities of recording broadband ground motion over a wide dynamic range provide insights into details of fracture processes at the earthquake source ( e.g. , Spudich and Cranswick 1984), the heterogeneity levels of the medium ( e.g. , Sato and Fehler 1998), site effects ( e.g. , Ansal 1999), and the spatial variability of earthquake ground motion ( e.g. , Abrahamson and Bolt 1987). In addition, their wide dynamic range provides the opportunity to investigate the transition of strong to weak motion, e.g. , earthquake source and ground motion scaling over a wide magnitude range ( e.g. , Halldorsson and Papageorgiou 2005). The sensitivity of the strong-motion instruments generally controls how far this range extends to smaller magnitudes. However, when the waveform correlation is sufficient over the aperture of a group of instruments operating in an array configuration, the sensitivity can be increased beyond that of the individual instruments via array processing techniques (Steinberg 1965). Therefore, it is essential that as many instruments as possible within the array capture any earthquake disturbances, even weak motion, because the application of array processing techniques can produce good data sets from otherwise less useful data ( e.g. , Almendros et al. 1999; Gibbons and Ringdal 2006). While it may seem straightforward to capture a complete set of earthquake recordings, in practice it is difficult due to the variability of ground motion and noise levels across even a small-aperture array, especially when the instruments use adaptive triggers (such as short-term vs. long-term average energy levels, STA:LTA), whose sensitivity is dependent on the current background noise levels. High-sensitivity instruments such as velocity meters generally trade off high-amplitude response for a low noise floor while strong-motion (accelerometer) sensors are capable of capturing the largest ground motion, even …

Enhancement of the National Strong-Motion Network in Turkey

Two arrays comprising 20 strong-motion sensors were established in western Turkey. The 14 stations of BYTNet follow a N-S trending line about 65 km in length, normal to strands of the North Anatolian fault that runs between the cities of Bursa and Yalova. Here the dominant character of the potential fault movement is a right-lateral transform slip. The DATNet array, comprising a total of eight stations, is arranged along a 110-km-long E-W trending direction along the Menderes River valley between Denizli and Aydin. (Two stations in this array were incorporated from the existing Turkish national strong-motion network.) This is an extensional tectonic environment, and the network monitors potential large normal-faulting earthquakes on the faults in the valley. The installation of the arrays was supported by the North Atlantic Treaty Organization (NATO) under its Science for Peace Program. Maintenance and calibration is performed by the General Directorate of Disaster Affairs (GDDA) according to a protocol between Middle East Technical University (METU) and GDDA. Many young engineers and scientists have been trained in network operation and evaluation during the course of the project, and an international workshop dealing with strong-motion instrumentation has been organized as part of the project activities.

Costs and Benefits of Improved Seismic Monitoring

Research Article| September 01, 2005 Costs and Benefits of Improved Seismic Monitoring Paul Somerville Paul Somerville URS Search for other works by this author on: GSW Google Scholar Seismological Research Letters (2005) 76 (5): 539–540. https://doi.org/10.1785/gssrl.76.5.539 Article history first online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Paul Somerville; Costs and Benefits of Improved Seismic Monitoring. Seismological Research Letters 2005;; 76 (5): 539–540. doi: https://doi.org/10.1785/gssrl.76.5.539 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietySeismological Research Letters Search Advanced Search I was a member of the National Research Council panel charged with the task of analyzing the costs and benefits of improved seismic monitoring (NRC, 2005). The main focus of the report was the Advanced National Seismic System (ANSS), a U.S. Geological Survey program authorized by Congress in 2000 whose implementation has proceeded at an appropriated annual funding level (approximately $4 million) that is about one tenth of the planned level. At this rate, it would take about 50 years to complete the planned implementation of ANSS. The plan for ANSS consists of equal numbers of strong-motion sensors... You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Geotechnical Characterization of TriNet Sites: A Status Report

The TriNet project, launched in 1997, created an improved, real-time seismic monitoring network in Southern California. Planning of the network began in 1995 (e.g., Heaton et al., 1996), building on the success of the earlier TERRAscope network, which included 24 digital broadband and strongmotion instruments throughout Southern California (e.g., Kanamori et al., 1993). At the end of the five-year TriNet project the network comprised 150 real-time digital broadband stations and another 400 strong-motion sensors, 50 of which were also real-time. This network is now recording digital broadband data for Southern California earthquakes at an unprecedented rate, data that are already proving valuable for investigations of earthquake sources and regional wave propagation, as well as earthquake response.

A Real-time Interactive Educational Seismology Exhibit

Modern seismology has rapidly passed the level of many educational displays. While seismologists almost exclusively use digital data, the traditional pen and ink drum recorder remains the mainstay of many educational seismology exhibits in museums. Although a drum recorder retains several major advantages, such as familiarity and visual appeal, it also has several clear disadvantages, both technical and educational. Chief among the technical disadvantages are the poor data quality of many museum displays due to high noise levels and the difficulty and cost of replacing paper, pens, and ink on a routine basis. The use of a drum recorder also gives a misleading and antiquated impression of how modern seismologists work. Another feature of museum displays is that the sensor is usually kept well away from the actual display to reduce seismic noise levels. However, having a sensor near the display is useful for adding interaction to the display. Visitors can create their own seismic signals by jumping, a feature which is especially popular with children. In general, interactivity in museum displays has been shown to increase the attractiveness of the display. Interactivity is believed to promote learning, at least for some learning styles, although it is not always clear exactly what is being learned (Feher, 1990; Falk and Dierking, 1992). In this paper we describe an innovative exhibit that provides interactivity, displays high-quality seismic data, and transmits the data in real-time to a local seismic network. A strong-motion sensor is located under the display, allowing people to jump, stamp feet, and otherwise create seismic waves that appear almost immediately on a computer monitor. During periods of little museum activity, which is at least 14 hours per day, the sensor records useful low-noise data that can be merged with regional seismic network data for scientific analysis. In addition …

Southern California Seismic Network: Caltech/USGS Element of TriNet 1997-2001

The California Institute of Technology (Caltech), the United States Geological Survey (USGS), and the California Department of Conservation, Division of Mines and Geology (CDMG) are completing the implementation of TriNet, a modern seismic information system for southern California. TriNet consists of two elements, the Caltech-USGS element and the CDMG element (Mori et al., 1998). The Caltech-USGS element (Caltech-USGS TriNet) concentrates on rapid notification and archiving of data for seismological applications, while the CDMG element is focused on the needs of engineering users (Hauksson et al., 2002). All three. TriNet agencies are working toward facilitating emergency response and long-term mitigation of earthquake hazards in cooperation with other agencies. The technical development of Caltech-USGS TriNet is sufficiently different from the CDMG element of TriNet to warrant a separate description. This paper provides a technical overview of the design principles of Caltech-USGS TriNet. These principles were based on a document that stated the scientific requirements of TriNet (Jones et al., 1997). We also describe the implementation of these principles using modern technology. The implementation consisted of station deployments, establishing communications links, and developing and implementing new hardware and software for data processing and information distribution. Thus, the Caltech-USGS TriNet is an integrated project extending across many disciplines, using basic ground-motion data and seismological algorithms to generate in near real-time a sophisticated earthquake knowledge base following earthquakes in southern California. Caltech-USGS TriNet applies advanced technology to record both small and large earthquakes on scale. The latest generation of broadband and strong-motion sensors with 24-bit digitizers is used to acquire high-fidelity ground-motion data. Real-time communication is a requirement to facilitate rapid processing and notification about seismicity for emergency management. The data acquisition systems are designed to ensure redundancy and automated processing of data. To accomplish automation, high-speed computers and advanced software form the inner workings of the Caltech-USGS TriNet system. Adopting the commercial database Oracle is an important foundation of our data management system. The automated flow of data into an accessible data center and the automatic population of the database is part of our new seismic network design and is an essential feature of Caltech-USGS TriNet. The TriNet real-time systems and database have been operating online for more than two years, processing real-time data currently from more than 375 stations, or more than 1,200 high sample-rate data channels. Many of these capabilities were tested in the 1999 M_w 7.1 Hector Mine earthquake. New postprocessing and catalog-generation approaches have also been implemented in 2001. Caltech-USGS TriNet is one of the first U.S. regional seismic networks that uses digital technology on a scale of 200 or more stations, with both broadband and strongmotion sensors. In comparison, the IRIS Global Seismic Network consists of 108 stations, with plans for a total of 150 stations (Hutt and Bolton, 1999). Previous digital networks, such as TERRAscope (Kanamori et al., 1997) and the Berkeley Digital Seismic Network (BDSN) (Gee et aL, 1996), have been smaller than TriNet, with about 20 stations each. TriNet also benefits from the experience of other seismic networks around the world. The K-Net in Japan is another example of large-scale deployment of a digital network, although it is focused on strong motions (Kinoshita, 1998). Extensive developments of strong-motion networks in Taiwan and associated near-real-time processing of data employ somewhat different technology but have similar goals for information products following large earthquakes (Teng et al., 1997).

One minute after: Strong-motion map, effective epicenter, and effective magnitude

Abstract This article reports the recent progress on real-time seismic monitoring in Taiwan, particularly the real-time strong-motion monitoring by the Taiwan Central Weather Bureau's telemetered seismic network (CWBSN), which is presently aiming at rapid reporting immediately after a large earthquake occurrence. If rapid reporting can be achieved before the arrival of the strong shaking, earthquake early warning will become possible. CWBSN has achieved the generation of the intensity map, epicenter, and magnitude within 1 min of the occurrence of a large earthquake. Both rapid reporting and early warning are principally applied to large (M ≫ 5) events; the requirement of on-scale waveform recording prompted CWBSN in 1995 to integrate strong-motion sensors (e.g., force-balance accelerometers) into its telemetered seismic monitoring system. Time-domain recursive processing is applied to the multi-channel incoming seismic signals by a group of networked personal computers to generate the intensity map. From the isoseismal contours, an effective epicenter is immediately identified that resides in the middle of the largest (usually the 100-gal) contour curve of the intensity map. An effective magnitude is also defined that can be derived immediately from the surface area covered by the largest (usually the 100-gal) contour curve. For a large event with a finite rupture surface, the epicenter and magnitude so derived are more adequate estimates of the source location and of the strength of destruction. The effective epicenter gives the center of the damage area; it stands in contrast with the conventional epicenter location, which only gives the initial point of rupture nucleation. The effective magnitude reflects more closely the earthquake damage potential, instead of the classical magnitude definition that emphasizes the total energy release. The CWBSN has achieved in obtaining the above crucial source information well within 1 min. This time can further be reduced to better than 30 sec, as illustrated by the example in this article, showing that earthquake early warning is indeed an achievable goal. The rapid reporting and early warning information is electronically transmitted to users to allow rapid response actions, with or without further human intervention.

The 1989–1990 seismic swarm in the Alban Hills volcanic area, central Italy

Abstract A long seismic swarm has been recorded by a digital microseismic network that the Istituto Nazionale di Geo- fisica (ING) deployed from April 1989 to March 1990 in the Alban Hills Quaternary volcanic region, about 20 km southeast of Rome. The network consisted of thirteen digital stations equipped with four six-component (weak motion and strong motion sensors), three three-component and six vertical weak motion seismometers, including both broad-band and short-period sensors. More than 3000 earthquakes were detected during about one year of operation. The data recorded during the sequence provided an unprecedented opportunity to resolve details of the seismogenic features of this area that has experienced earthquakes since the Roman age. Although the temporal distribution of seismicity reveals a volcanic-type swarm activity, the recorded seismic signals show medium-high frequency waveforms and clear S-wave arrivals typical of tectonic earthquakes. About 1100 earthquakes in a magnitude range between M D ~ 1.5 and MD~ 4.0 have been located. The seismicity delineates a ~ 6 × 12 km 2 NW- SE-elongated region that corresponds to the area where the most recent (0.027 Ma) phreato-magmatic activity took place. Almost no earthquakes occurred beneath the central cone and the eastern side of the caldera. The seismicity is shallow and is mostly concentrated in two clusters that are offset laterally and are at sligthly different depths (3-5 and 4-6 km). The fault plane solutions of the strongest earthquakes reveal a ~ NE-SW extension, consistent with the regional orientation of the stress field along the Apenninic chain as obtained by other seismo- logical data.