ICBM—Integrated Combined Baseline Modification: An Algorithm for Segmented Baseline Estimation

Abstract Accelerograms are the primary source for characterizing strong ground motion. It is therefore of paramount interest to have high‐quality recordings free from any nonphysical contamination. Frequently, accelerograms are affected by baseline jumps and drifts, either related to the instrument and/or a major earthquake. In this work, I propose a correction method for these undesired baseline drifts based on segmented linear least squares. The algorithm operates on the integrated waveforms and combines all three instrument components to estimate a model that modifies the baseline to be at zero continuously. The procedure consists of two steps: first a suite of models with variable numbers of discontinuities is derived for all three instrument components. During this process, the number of discontinuities is reduced in a parsimonious way, for example, two very close discontinuities are merged into a single one. In the second step, the optimal model is selected on the basis of the Bayesian information criterion. I exemplify the application on synthetic waveforms with known discontinuities and on observed waveforms from a unified strong‐motion database of the Japan Meteorological Agency (JMA) and the National Research Institute for Earth Science and Disaster Prevention (NIED, Japan) networks for the major events of the 2016 Kumamoto earthquakes. After the baseline jump correction, the waveforms are furthermore corrected for displacement according to Wang et al. (2011). The resulting displacements are comparable to the Interferometric Synthetic Aperture Radar‐derived displacement estimates for the Kumamoto earthquake sequence.

Download Full-text

Deep learning for bias correction of MJO prediction

Nature Communications ◽

10.1038/s41467-021-23406-3 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

H. Kim ◽

Y. G. Ham ◽

Y. S. Joo ◽

S. W. Son

Keyword(s):

Deep Learning ◽

Bias Correction ◽

Numerical Models ◽

Weather Prediction ◽

Primary Source ◽

Correction Method ◽

Prediction Skill ◽

Convective System ◽

Forecast Errors ◽

Potential Predictability

AbstractProducing accurate weather prediction beyond two weeks is an urgent challenge due to its ever-increasing socioeconomic value. The Madden-Julian Oscillation (MJO), a planetary-scale tropical convective system, serves as a primary source of global subseasonal (i.e., targeting three to four weeks) predictability. During the past decades, operational forecasting systems have improved substantially, while the MJO prediction skill has not yet reached its potential predictability, partly due to the systematic errors caused by imperfect numerical models. Here, to improve the MJO prediction skill, we blend the state-of-the-art dynamical forecasts and observations with a Deep Learning bias correction method. With Deep Learning bias correction, multi-model forecast errors in MJO amplitude and phase averaged over four weeks are significantly reduced by about 90% and 77%, respectively. Most models show the greatest improvement for MJO events starting from the Indian Ocean and crossing the Maritime Continent.

Download Full-text

The Effect of Type and Height of Piers on the Seismic Behavior of Reinforced Concrete Bridges

International Journal of Engineering Research in Africa ◽

10.4028/www.scientific.net/jera.41.79 ◽

2019 ◽

Vol 41 ◽

pp. 79-87 ◽

Cited By ~ 2

Author(s):

Mohamed Cherif Djemai ◽

Mahmoud Bensaibi ◽

Fatma Zohra Halfaya

Keyword(s):

Reinforced Concrete ◽

Structural Parameters ◽

Strong Motion ◽

Concrete Bridges ◽

Geometrical Parameters ◽

Girder Bridges ◽

Building Research Institute ◽

Reinforced Concrete Bridges ◽

Dynamic Analyses ◽

Strong Motion Database

Bridges are commonly used lifelines; they play an important role in the economic activity of a city or a region and their role can be crucial in a case of a seismic event since they allow the arrival of the first aid. Reinforced concrete (RC) bridges are worldwide used type view their durability, flexibility and economical cost. In fact, their behavior under seismic loading was the aim of various studies. In the present study the effect of two structural parameters i.e. the height and the type of piers of reinforced concrete bridges on seismic response is investigated. For that reason, different multi-span continuous girder bridges models with various geometrical parameters are considered. Then, non-linear dynamic analyses are performed based on two types of piers which are: multiple columns bent and wall piers with varying heights. In this approach, a serie of 40 ground motions records varying from weak to strong events selected from Building Research Institute (BRI) strong motion database are used including uncertainty in the soil and seismic characteristics. Modelling results put most emphasis on the modal periods and responses of the top pier displacements, they show the influence of the considered parameters on the behavior of such structures and their impact on the strength of reinforced concrete bridges.

Download Full-text

The Engineering Strong‐Motion Database: A Platform to Access Pan‐European Accelerometric Data

Seismological Research Letters ◽

10.1785/0220150278 ◽

2016 ◽

Vol 87 (4) ◽

pp. 987-997 ◽

Cited By ~ 38

Author(s):

Lucia Luzi ◽

Rodolfo Puglia ◽

Emiliano Russo ◽

Maria D'Amico ◽

Chiara Felicetta ◽

...

Keyword(s):

Strong Motion ◽

Strong Motion Database

Download Full-text

Seismic Response of Embankment Dams Based on Recorded Strong-Motion Data in Japan

Earthquake Spectra ◽

10.1193/042918eqs107m ◽

2019 ◽

Vol 35 (2) ◽

pp. 955-976 ◽

Cited By ~ 2

Author(s):

DongSoon Park ◽

Tadahiro Kishida

Keyword(s):

Time Series ◽

Seismic Response ◽

Prediction Models ◽

Strong Motion ◽

Dynamic Responses ◽

Design Stage ◽

Ground Acceleration ◽

Motion Data ◽

Embankment Dams ◽

Strong Motion Database

It is important to investigate strong-motion time series recorded at dams to understand their complex seismic responses. This paper develops a strong-motion database recorded at existing embankment dams and analyzes correlations between dam dynamic responses and ground-motion parameters. The Japan Commission on Large Dams database used here includes 190 recordings at the crests and foundations of 60 dams during 54 earthquakes from 1978 to 2012. Seismic amplifications and fundamental periods from recorded time series were computed and examined by correlation with shaking intensities and dam geometries. The peak ground acceleration (PGA) at the dam crest increases as the PGA at the foundation bedrock increases, but their ratio gradually decreases. The fundamental period broadly increases with the dam height and PGA at the foundation bedrock. The nonlinear dam response becomes more apparent as the PGA at the foundation bedrock becomes >0.2 g. The prediction models of these correlations are proposed for estimating the seismic response of embankment dams, which can inform the preliminary design stage.

Download Full-text

Development of a New Method of Baseline Correction on Earthquake Strong Motions and Its Application to Long Period Sloshing Responses of Liquid Storage Tanks During Strong Earthquakes

Seismic Engineering ◽

10.1115/pvp2003-2121 ◽

2003 ◽

Author(s):

Chikahiro Minowa

Keyword(s):

Ground Motion ◽

Low Frequency ◽

Strong Motion ◽

Correction Method ◽

New Method ◽

Baseline Correction ◽

Storage Tanks ◽

Low Frequencies ◽

Long Period ◽

Liquid Storage

In this paper, a new method of baseline correction on strong motion acceleration records is presented and the fundamental concept for baseline corrections on the earthquake strong motions is described. Considering the filtering effect, the earthquakes ground motion displacements of 1995 JMA KOBE, 1999 Kocaeli YPT and 1999 Chi-Chi TCU068 are discussed. Also, the linear sloshing responses of large liquid tanks subjected to these motions were discussed. Since liquid storage tanks show the low frequency (long period) sloshing characteristics and the strong motion characteristics of 1999 Kocaeli and Chi-Chi earthquakes are also low frequencies and large permanent displacements, the sloshing responses in large liquid tanks, especially in long natural periods, were significantly affected by the low frequency motions (large permanent displacements) of these devastating earthquakes. It is very important to use suitable ground motion characterized low frequency content for earthquake resistant design of liquid storage tanks. The baseline correction method presented in the paper may be adequately used to correct strong motion records for large liquid storage design.

Download Full-text