Magnitude Calculation without Saturation from Strong-Motion Waveforms

2020 ◽  
Author(s):  
Zhang Hongcai ◽  
Diego Melgar ◽  
Dara E. Goldberg
Keyword(s):  
Real Time ◽  
Near Field ◽  
Magnitude Estimate ◽  
Strong Motion ◽  
Global Navigation Satellite Systems ◽  
Coseismic Deformation ◽  
Ground Displacement ◽  
Strong Motion Records ◽  
Satellite Systems ◽  
Global Navigation Satellite

ABSTRACT After destructive earthquakes, it is a challenge to estimate magnitude rapidly and accurately for dissemination to emergency responders and the public. Here, we propose criteria to calculate peak ground displacement (PGD) from strong-motion records, which can be used to calculate unsaturated event magnitude. Using collocated strong-motion and Global Navigation Satellite Systems observations of five major earthquakes in Japan, we demonstrate the effectiveness and accuracy of our strategy. Our results show that, with the right filtering criteria, PGD estimated from strong-motion acceleration waveforms is consistent with geodetic estimates. The methodology, however, does not allow for calculation of reliable estimates of coseismic deformation or other ground displacement metrics. We demonstrate a simulated real-time magnitude estimation that suggests it is feasible to generate an unsaturated magnitude estimate in real time from near-field strong-motion records. These findings have important implications for early warning and emergency response in seismically active areas, especially where real-time strong-motion data are more widely available than geodetic measurements.

Automatic Extraction of Permanent Ground Offset from Near-Field Accelerograms: Algorithm, Validation, and Application to the 2004 Parkfield Earthquake

2020 ◽  
Vol 110 (6) ◽  
pp. 2638-2646
Author(s):  
Asaf Inbal ◽  
Alon Ziv
Keyword(s):  
Near Field ◽  
Strong Motion ◽  
Fault Slip ◽  
Global Navigation Satellite Systems ◽  
New Approach ◽  
Satellite Systems ◽  
Spatial Coverage ◽  
Parkfield Earthquake ◽  
Seismic Moment Release ◽  
Global Navigation Satellite

ABSTRACT Permanent ground offsets, constituting a prime dataset for constraining final fault-slip distributions, may not be recovered straightforwardly by double integration of near-field accelerograms due to tilt and other distorting effects. Clearly, if a way could be found to recover permanent ground offsets from acceleration records, then static datasets would be enlarged, and thus the resolution of fault-slip inversions would be enhanced. Here, we introduce a new approach for extracting permanent offsets from near-field strong-motion accelerograms. The main advantage of the new approach with respect to previous ones is that it corrects for source time functions of any level of complexity. Its main novelty is the addition of a constraint on the slope of the ground velocity spectra at long periods. We validated the new scheme using collocated accelerograms and Global Navigation Satellite Systems (GNSS) records of the 2011 Mw 9 Tohoku-Oki earthquake. We find a good agreement between accelerogram-based and GNSS-based ground offsets over a range of 0.1–5 m. To improve the spatial coverage of permanent ground offsets associated with the 2004 Parkfield earthquake, near-field accelerograms were baseline corrected using the new scheme. Static slip inversion of the combined GNSS-based and accelerogram-based ground displacements indicates appreciable seismic moment release south of the epicenter, about 5 km into the Cholame section of the San Andreas fault. We conclude that the strong shaking observed to the south of the epicenter is directly related to the slip in that area and is not the result of local amplification.

scholarly journals Asynchronous RTK Method for Detecting the Stability of the Reference Station in GNSS Deformation Monitoring

Sensors ◽  
2020 ◽  
Vol 20 (5) ◽  
pp. 1320
Author(s):  
Yuan Du ◽  
Guanwen Huang ◽  
Qin Zhang ◽  
Yang Gao ◽  
Yuting Gao
Keyword(s):  
Real Time ◽  
Reference Frame ◽  
Deformation Monitoring ◽  
Global Navigation Satellite Systems ◽  
Reference Station ◽  
Monitoring Station ◽  
Landslide Monitoring ◽  
Satellite Systems ◽  
Local Reference ◽  
Global Navigation Satellite

The real-time kinematic (RTK) positioning technique of global navigation satellite systems (GNSS) has been widely used for deformation monitoring in the past several decades. The RTK technique can provide relative displacements in a local reference frame defined by a highly stable reference station. However, the traditional RTK solution does not account for reference stations that experience displacement. This presents a challenge for establishing a near real-time GNSS monitoring system, as since the displacement of a reference station can be easily misinterpreted as a sign of rapid movement at the monitoring station. In this study, based on the reference observations in different time domains, asynchronous and synchronous RTK are proposed and applied together to address this issue, providing more reliable displacement information. Using the asynchronously generated time difference of a reference frame, the proposed approach can detect whether a measured displacement has occurred in the reference or the monitoring station in the current epoch. This allows for the separation of reference station movements from monitoring station movements. The results based on both simulated and landslide monitoring data demonstrate that the proposed method can provide reliable displacement determinations, which are critical in deformation monitoring applications, such as the early warning of landslides.

scholarly journals Reliable and Redundant RTK Positioning for Applications in Hard Observational Conditions

2012 ◽  
Vol 47 (1) ◽  
pp. 23-33 ◽  
Author(s):  
M. Bakuła ◽  
R. Pelc-Mieczkowska ◽  
M. Walawski
Keyword(s):  
Real Time ◽  
Computer Software ◽  
Global Navigation Satellite Systems ◽  
Advanced Technique ◽  
New Approach ◽  
Satellite Systems ◽  
The Common ◽  
Global Navigation Satellite ◽  
Forest Conditions

Reliable and Redundant RTK Positioning for Applications in Hard Observational ConditionsIt is well known that RTK (Real Time Kinematic) positioning is a very efficient technique for determination of coordinates in real time, directly on location. Although this technique has been well known since the mid-nineties of the last century, the common use of this technique developed since permanent reference GNSS (Global Navigation Satellite Systems) stations started operating as the national reference systems. Positioning in real time is very convenient for users who do not need to know any advanced technique of post-processing, especially in cases when no obstructions exist around the measured point exist. However, in practice, there are some situations when the use of RTK technique makes some difficulties, especially if the GNSS receiver has no full availability of satellites. Obstructions caused by trees, buildings, power lines etc. limit satellite availability and in consequence decrease the reliability of determined coordinates significantly. In those situations gross errors of even meters can appear in RTK positioning. In order to avoid misleading coordinates occurring we can use more than one RTK receiver simultaneously. The paper presents an approach to the RTK technology based on the simultaneous use of three different RTK receivers. Three different GNSS/RTK receivers can be set on a special mounting beam and additionally RTK positions are sent in real time to a computer. The computer software analyses not only the precision but also checks the accuracy and reliability of the RTK positions determined. Consequently, the new approach to RTK survey presented can allow obtaining reliable coordinates of centimeter accuracy even under very severe forest conditions.

scholarly journals Monitoramento estrutural em obras viárias utilizando a técnica RTK/NTRIP: Análise dos dados, desenvolvimento e implementação de um sistema de alerta posicional

2021 ◽  
Vol 10 (8) ◽  
pp. e3410816846
Author(s):  
Fabiane de Fátima Maciel ◽  
Herida dos Reis Silva ◽  
Fábio Luiz Albarici ◽  
Luciano Aparecido Barbosa ◽  
Jorge Luiz Alves Trabanco
Keyword(s):  
Real Time ◽  
Global Navigation Satellite Systems ◽  
Navigation Satellite ◽  
Satellite Systems ◽  
Real Time Kinematic ◽  
Global Navigation ◽  
Global Navigation Satellite

Desde a ampliação do sistema rodoviário no Brasil na década de 1930, tem-se um cenário com inúmeras obras viárias em diferentes condições de uso e segurança. Tal fato é preocupante devido à falta de monitoramento adequado em OAEs (Obras de Arte Especiais) e por quem de fato estas estruturas devem ser monitoradas. Estas estruturas estão sujeitas às ações de forças estáticas e dinâmicas, podendo causar deslocamentos e/ou deformações que se caracterizam por sua amplitude, direção e comportamento temporal. Há também processos de deteriorações, sejam por desgaste ao uso ou por solicitações naturais, levando-se ao enfraquecimento da estrutura. A incorporação de métodos de inspeção e monitoramento no comportamento estrutural em OAEs torna-se crescente devido ao alto custo de recuperação destas obras. Contudo, é necessário que haja um plano de monitoramento contínuo ou periódico, de acordo com as grandezas admissíveis de cada estrutura. A tecnologia dos GNSS (Global Navigation Satellite Systems) por meio da metodologia de levantamento RTK (Real Time Kinematic), mostrou-se capaz de oferecer suporte em tempo real no controle de deformações estruturais. Neste contexto, foi desenvolvido o SiGE (Sistema de Gerenciamento Estrutural) para monitoramento e emissão de alertas acerca de eventos previamente determinados pelo operador do sistema. Com a obtenção destes dados em tempo real, é possível avaliar a segurança da estrutura em serviço, monitorar a estrutura de forma contínua e segura e aprimorar projetos futuros com a definição de deslocamentos estruturais máximos.

Solar radio burst interference index dedicated to GNSS single and double frequency users

2020 ◽  
Author(s):  
Jean-Marie Chevalier ◽  
Nicolas Bergeot ◽  
Pascale Defraigne ◽  
Christophe Marque ◽  
Elisa Pinat
Keyword(s):  
Real Time ◽  
Solar Radio ◽  
Global Navigation Satellite Systems ◽  
Civil Aviation ◽  
International Gnss Service ◽  
Satellite Systems ◽  
Double Frequency ◽  
Weather Events ◽  
Gnss Measurements ◽  
Global Navigation Satellite

<p>Intense solar radio bursts (SRBs) emitted at L-band frequencies are a source of radio frequency interference for Global Navigation Satellite Systems (GNSS) by inducing a noise increase in GNSS measurements, and hence degrading the carrier-to-noise density (C/N<sub>0</sub>). Such space weather events are critical for GNSS-based applications requiring real-time high-precision positioning.</p><p>Since 2015, the Royal Observatory of Belgium (ROB) monitors in near real-time the C/N<sub>0</sub> observations from the European Permanent Network (EPN). The monitoring allows to detect accurately the general fades of C/N<sub>0</sub> due to SRBs over Europe as from 1 dB-Hz. It provides in near real-time a quantification of the GNSS signal reception fade for the L1 C/A and L2 P(Y) signals and notifies civilian single and double frequency users with a 4-level index corresponding to the potential impact on their applications. This service is part of the real-time monitoring service of the PECASUS project of the International Civil Aviation Organization (ICAO) which started end of 2019.</p><p>Results of this 5-year monitoring will be discussed, including the 3 SRBs of 2015 and 2017, together with the new developments toward a global index using the International GNSS Service (IGS) network. In addition, we will show how the SRB monitoring is sometimes interfered by GPS flex power campaigns on the satellites from blocks IIR-M and IIF, and how it is mitigated . The routine and transient GPS flex power campaigns will be presented in terms of C/N<sub>0</sub> variations for the EPN and IGS networks.</p>

Slip Complementarity and Triggering between the Foreshock, Mainshock, and Afterslip of the 2019 Ridgecrest Rupture Sequence

2020 ◽  
Vol 110 (4) ◽  
pp. 1701-1715 ◽  
Author(s):  
Qiang Qiu ◽  
Sylvain Barbot ◽  
Teng Wang ◽  
Shengji Wei
Keyword(s):  
Joint Inversion ◽  
Stress Transfer ◽  
Strong Motion ◽  
Global Navigation Satellite Systems ◽  
Fault System ◽  
Coseismic Slip ◽  
Satellite Systems ◽  
The North ◽  
Global Navigation Satellite ◽  
Lower Crustal

ABSTRACT We investigate the deformation processes during the 2019 Ridgecrest earthquake sequence by combining Global Navigation Satellite Systems, strong-motion, and Interferometric Synthetic Aperture Radar datasets in a joint inversion. The spatial complementarity of slip between the Mw 6.4 foreshock, Mw 7.1 mainshock, and afterslip suggests the importance of static stress transfer as a triggering mechanism during the rupture sequence. The coseismic slip of the foreshock concentrates mainly on the east-northeast–west-southwest fault above the hypocenter at depths of 2–8 km. The slip distribution of the mainshock straddles the region above the hypocenter with two isolated patches located to the north-northwest and south-southeast, respectively. The geodetically determined moment magnitudes of the foreshock and mainshock are equivalent to moment magnitudes Mw 6.4 and 7.0, assuming a rigidity of 30 GPa. We find a significant shallow slip deficit (>60%) in the Ridgecrest ruptures, likely resulting from the immature fault system in which the sequence occurred. Rapid afterslip concentrates at depths of 2–6 km, surrounding the rupture areas of the foreshock and mainshock. The ruptures also accelerated viscoelastic flow at lower-crustal depths. The Garlock fault was loaded at several locations, begging the question of possible delayed triggering.

scholarly journals QUICK 3D WITH UAV AND TOF CAMERA FOR GEOMORPHOMETRIC ASSESSMENT

2020 ◽  
Vol XLIII-B1-2020 ◽  
pp. 259-264
Author(s):  
A. Masiero ◽  
G. Sofia ◽  
P. Tarolli
Keyword(s):  
High Resolution ◽  
Real Time ◽  
Low Cost ◽  
Wide Band ◽  
Global Navigation Satellite Systems ◽  
3D Reconstructions ◽  
Satellite Systems ◽  
Close Range ◽  
Tof Camera ◽  
Global Navigation Satellite

Abstract. Most of the high resolution topographic models are currently obtained either by means of Light Detection and Ranging (LiDAR) or photogrammetry: the former is usually preferred for producing very accurate models, whereas the latter is much more frequently used in low cost applications. In particular, the availability of more affordable Unmanned Aerial Vehicles (UAVs) equipped with high resolution cameras led to a dramatic worldwide increase of UAV photogrammetry-based 3D reconstructions. Nevertheless, accurate high resolution photogrammetric reconstructions typically require quite long data processing procedures, which make them less suitable for real-time applications.This work aims at investigating the use of a low cost Time of Flight (ToF) camera, combined with an Ultra-Wide Band (UWB) positioning system, mounted on a drone, in order to enable quasi real time 3D reconstructions of small to mid-size areas, even in locations where Global Navigation Satellite Systems (GNSSs) are not available.The proposed system, tested on a small area on the Italian Alps, provided high resolution mapping results, with an error of few centimeters with respect to a terrestrial close-range photogrammetry survey conducted on the same day.

scholarly journals Study the capabilities of RTK Multi GNSS under forest canopy in regions of Indonesia

2019 ◽  
Vol 94 ◽  
pp. 01021 ◽  
Author(s):  
Heri Andreas ◽  
Hasanuddin Zainal Abidin ◽  
Dina Anggreni Sarsito ◽  
Dhota Pradipta
Keyword(s):  
Real Time ◽  
Forest Canopy ◽  
Global Navigation Satellite Systems ◽  
Navigation Satellite ◽  
Satellite Systems ◽  
Position Accuracy ◽  
The Earth ◽  
Real Time Kinematic ◽  
The Future ◽  
Global Navigation Satellite

For more than two decade, the position on the earth can be precisely determined “real-time” in the order of few centimeters by Real Time Kinematic (RTK) GNSS (Global Navigation Satellite Systems) Method. Nevertheless, few limitations are still recognized such as degradation of accuracy against limited satellite visibilities (e.g. heavy satellite obstructions from forest canopy). It usually takes time to resolve the ambiguities or even in many occasion resulted in failure. Fortunately since recent years to the future seems more satellite systems beside GPS and GLONASS are being launched such as BEIDOU, GALILEO, QZSS, etc. It means that more satellite will be existed above the sky. The term GNSS has changed into Multi GNSS. This Multi GNSS is theoretically adding the value to previous GNSS System like GPS; problems of limited satellite visibilities (e.g. under forest canopy) to the position accuracy perhaps will reduce. Within this paper we try to do study the capabilities of RTK Multi GNSS under forest canopy in Indonesia. We observed by RTK in the forest areas which have canopy of 40 to 90 percent. As conclusion we found improvement in positioning result of even area of very limited satellite visibilities.

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