scholarly journals Seismic Damage Accumulation in Highway Bridges in Earthquake-Prone Regions

2015 ◽  
Vol 31 (1) ◽  
pp. 115-135 ◽  
Author(s):  
Jayadipta Ghosh ◽  
Jamie E. Padgett ◽  
Mauricio Sánchez-Silva
Keyword(s):  
Service Life ◽  
Damage Accumulation ◽  
Main Shock ◽  
Prediction Models ◽  
Time Window ◽  
Damage Index ◽  
Active Regions ◽  
Highway Bridges ◽  
Main Shocks ◽  
Aftershock Sequences

Civil infrastructures, such as highway bridges, located in seismically active regions are often subjected to multiple earthquakes, including multiple main shocks during their service life or main shock–aftershock sequences. Repeated seismic events result in reduced structural capacity and may lead to bridge collapse, causing disruption in the normal functioning of transportation networks. This study proposes a framework to predict damage accumulation in structures subjected to multiple shock scenarios after developing damage index prediction models and accounting for the probabilistic nature of the hazard. The versatility of the proposed framework is demonstrated on a case-study highway bridge located in California for two distinct hazard scenarios: (1) multiple main shocks during the service life and (2) multiple aftershock earthquake occurrences following a single main shock. Results reveal that in both cases there is a significant increase in damage index exceedance probabilities due to repeated shocks within the time window of interest.

Seismotectonics of the northern Longitudinal Valley, Taiwan, inferred from aftershock sequences of 2018 Mw6.4 and 2019 Mw6.2 Hualien earthquakes

2020 ◽  
Author(s):  
Wei-Fang Sun ◽  
Hao Kuo-Chen ◽  
Zhuo-Kang Guan ◽  
Wen-Yen Chang
Keyword(s):  
Main Shock ◽  
Surface Deformation ◽  
Plate Boundary ◽  
Aftershock Sequence ◽  
Tectonic Structures ◽  
Seismicity Rate ◽  
Transitional Area ◽  
Main Shocks ◽  
Aftershock Sequences ◽  
Seismic Networks

<p>In the Hualien area, two Mw6.4 and Mw6.2 earthquakes, 20 km apart, occurred in February 2018 and April 2019 respectively. The former to the northeast, located offshore to ​​the Liwu river, triggered several earthquake clusters along the Milun fault and southward to the Longitudinal Valley, the suture of the Eurasian and the Philippine Sea plates; the latter to the southwest, located in the Central Range, also triggered several seismic swarms in the Central Range,  along the Liwu river to the northeast and at Ji'an to the southeast. Except for the Milun fault, neither GPS nor InSAR observations detects significant surface deformation after the occurrence of these two main shocks, indicating that the earthquake ruptures mainly developed within the crust. Therefore, seismic observation becomes an efficient tool for revealing the seismotectonics of the two earthquake sequences. For monitoring the aftershock sequences, two days after the main shocks, we deployed two geophone arrays, 70 Z-component RefTek 125A TEXANs for two weeks in 2018 and 47 three-component Fairfield Nodal Z-Lands for one month in 2019, with 1-5 km station spacing around the Hualien City. These earthquake swarms were well recorded and analyzed through the dense seismic networks. The numbers of aftershock sequences manually identified are two-fold more than that issued by the Central Weather Bureau, Taiwan. The seismicity of the 2018 aftershock sequence, to depths of between 5-15 km, was significantly reduced within 10 days after the main shock. however, the seismicity of the 2019 aftershock sequence, to depths of between 2-50 km, was still above background seismicity rate 30 days after the main shock. The spatial distribution of the 2018 aftershock sequence could be related to a fault zone of the plate boundary, but that of the 2019 and the relocated 1986 aftershock sequences show a conjugate thrust fault pair beneath the eastern Central Range. Our results clearly depict several local tectonic structures that have not been observed at the northern tip of the Longitudinal Valley, not only a suture but also a transitional area from collision to subduction.</p>

Damage Assessment of RC Frame Structures under Multi-Earthquake Sequences

2012 ◽  
Vol 446-449 ◽  
pp. 739-744 ◽  
Author(s):  
Wei Huang ◽  
Jiang Qian ◽  
Bin Bin Zhuang ◽  
Qiu Shi Fu
Keyword(s):  
Damage Assessment ◽  
Damage Accumulation ◽  
Damage Index ◽  
Rc Frame ◽  
Damage State ◽  
Lateral Drift ◽  
Seismic Sequences ◽  
Aftershock Sequences ◽  
Rc Frame Structures ◽  
Earthquake Sequences

This paper presents the results of a numerical investigation aimed at evaluation of damage accumulation in structures under different seismic sequences. For this purpose, a multi-story RC frame model representing the typical buildings was built and subjected to four sets of different repeating seismic sequences with different magnitude. The results indicate that the aftershock sequences will increase the damage accumulation in structures, and the damage index based on the Park and Ang model can qualitatively and quantitatively ascertain the damage state of the structure instead of the single index based on the lateral drift demands. Additionally, different sequences with the identical energy input will cause the same damage state in structures.

The foreshock sequence of the 1986 Chalfant, California, earthquake

1988 ◽  
Vol 78 (1) ◽  
pp. 172-187
Author(s):  
Kenneth D. Smith ◽  
Keith F. Priestley
Keyword(s):  
Main Shock ◽  
Slip Surface ◽  
Body Waves ◽  
Aftershock Distribution ◽  
Time Period ◽  
Main Shocks ◽  
Short Period ◽  
Local Shear ◽  
Stress Drops ◽  
Foreshock Activity

Abstract The ML 6.4 Chalfant, California, earthquake of 21 July 1986 was preceded by an extensive foreshock sequence. Foreshock activity is characterized by shallow clustering activity, including 7 events greater than ML 3, beginning 18 days before the earthquake, an ML 5.7 foreshock 24 hr before the main shock that ruptured only in the upper 10 km of the crust, and an “off-fault” cluster of activity perpendicular to the slip surface of the ML 5.7 foreshock associated with the hypocenter of the main shock. The Chalfant sequence occurred within the local short-period network, and the spatial and temporal development of the foreshock sequence can be observed in detail. Seismicity of the July 1986 time period is largely confined to two nearly conjugate planes; one striking N30°E and dipping 60° to the northwest associated with the ML 5.7 foreshock and the other striking N25°W and dipping 70° to the southwest associated with the main shock. Focal mechanisms for the foreshock period fall into two classes in agreement with these two planes. Shallow clustering of earthquakes in July and the ML 5.7 principal foreshock occur at the intersection of the two planes at a depth of approximately 7 km. The seismic moments determined from inversion of the teleseismic body waves are 4.2 × 1025 and 2.5 × 1025 dyne-cm for the principal foreshock and the main shock, respectively. Slip areas for these two events can be estimated from the aftershock distribution and result in stress drops of 63 bars for the principal foreshock and 16 bars for the main shock. The main shock occurred within an “off-fault” cluster of earthquakes associated with the principal foreshock. This cluster of activity occurs at a predicted local shear stress high in relation to the slip surface of the 20 July earthquake, and this appears to be the triggering mechanism of the main shock. The shallow rupture depth of the principal foreshock indicates that this event was anomalous with respect to the character of main shocks in the region.

Estimates of velocity structure and source depth using multiple P waves from aftershocks of the 1987 Elmore Ranch and Superstition Hills, California, earthquakes

1991 ◽  
Vol 81 (2) ◽  
pp. 508-523
Author(s):  
Jim Mori
Keyword(s):  
Velocity Structure ◽  
Velocity Model ◽  
P Wave ◽  
Sediment Layer ◽  
Source Depth ◽  
Imperial Valley ◽  
P Waves ◽  
Main Shocks ◽  
Aftershock Sequences ◽  
Event Record

Abstract Event record sections, which are constructed by plotting seismograms from many closely spaced earthquakes recorded on a few stations, show multiple free-surface reflections (PP, PPP, PPPP) of the P wave in the Imperial Valley, California. The relative timing of these arrivals is used to estimate the strength of the P-wave velocity gradient within the upper 5 km of the sediment layer. Consistent with previous studies, a velocity model with a value of 1.8 km/sec at the surface increasing linearly to 5.8 km/sec at a depth of 5.5 km fits the data well. The relative amplitudes of the P and PP arrivals are used to estimate the source depth for the aftershock distributions of the Elmore Ranch and Superstition Hills main shocks. Although the depth determination has large uncertainties, both the Elmore Ranch and Superstition Hills aftershock sequences appear to have similar depth distribution in the range of 4 to 10 km.

Durability design of composite bridges with given life in seasonal freezing region

2021 ◽  
Author(s):  
Xuefei Shi ◽  
Qi Xu
Keyword(s):  
Service Life ◽  
Life Cycle Cost ◽  
Mechanical Performance ◽  
Design Method ◽  
Protective Layer ◽  
Highway Bridges ◽  
Seasonal Freezing ◽  
Durability Design ◽  
Composite Bridges ◽  
Design Requirements

<p>Steel-concrete composite bridges are currently widely used in highway bridges in China. To reduce durability problems in seasonal freezing region, a design method with given service life is used. The service life is given on the basis of the environment condition and design requirements; then the structural design and safety analysis are carried out, and the durability design and analysis of the structural components are conducted. With the consideration of the mechanical performance, construction convenience and life-cycle cost, the structural scheme for bridges using twin-I girders, cross beams and precast full-width deck is recommended. Weather resistant steel is recommended to be used in nonmarine seasonal freezing regions with stabilization treatment, waterproof and drainage design, local anti-corrosion coating. Finally, a design process considering material, protective layer thickness and construction control is proposed to improve concrete deck durability.</p>

scholarly journals Complex networks of earthquakes and aftershocks

2005 ◽  
Vol 12 (1) ◽  
pp. 1-11 ◽  
Author(s):  
M. Baiesi ◽  
M. Paczuski
Keyword(s):  
Complex Networks ◽  
Time Windows ◽  
Scaling Law ◽  
Relative Strength ◽  
Modern Theory ◽  
Significant Information ◽  
Data Set ◽  
Scale Free ◽  
Main Shocks ◽  
Aftershock Sequences

Abstract. We invoke a metric to quantify the correlation between any two earthquakes. This provides a simple and straightforward alternative to using space-time windows to detect aftershock sequences and obviates the need to distinguish main shocks from aftershocks. Directed networks of earthquakes are constructed by placing a link, directed from the past to the future, between pairs of events that are strongly correlated. Each link has a weight giving the relative strength of correlation such that the sum over the incoming links to any node equals unity for aftershocks, or zero if the event had no correlated predecessors. A correlation threshold is set to drastically reduce the size of the data set without losing significant information. Events can be aftershocks of many previous events, and also generate many aftershocks. The probability distribution for the number of incoming and outgoing links are both scale free, and the networks are highly clustered. The Omori law holds for aftershock rates up to a decorrelation time that scales with the magnitude, m, of the initiating shock as tcutoff~10β m with β~-3/4. Another scaling law relates distances between earthquakes and their aftershocks to the magnitude of the initiating shock. Our results are inconsistent with the hypothesis of finite aftershock zones. We also find evidence that seismicity is dominantly triggered by small earthquakes. Our approach, using concepts from the modern theory of complex networks, together with a metric to estimate correlations, opens up new avenues of research, as well as new tools to understand seismicity.

scholarly journals Estimation Method of Maximum Inter-Story Drift Angle of Wood-Frame House using Two Accelerometers

2021 ◽  
Keyword(s):  
Health Monitoring ◽  
Main Shock ◽  
Integration Method ◽  
Damage Index ◽  
Estimation Method ◽  
High Accuracy ◽  
2016 Kumamoto Earthquake ◽  
Drift Angle ◽  
Story Drift ◽  
Wood Frame

Abstract. In April 2016, Kumamoto earthquake occurred in Japan and many wooden houses collapsed and many lives were lost because of the second and larger main shock. As a result, the need for Structural Health Monitoring (SHM) for wooden houses is receiving increased attention. In the SHM system, maximum inter-story drift angle is considered as the damage index. We assume that the first story of a wooden house will be damaged so that we need only to focus on the response of this first story. Hence, we install accelerometers on the ground floor and the second floor. In order to estimate the inter-story drift angle, we need to integrate the acceleration records twice. The simple double integration will result in erroneous results. Thus, in this paper, we propose the most appropriate integration method to estimate the maximum story drift angle with high accuracy using two accelerometers.

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