Effect of Fault Rupture Characteristics on Near-Fault Strong Ground Motions

Understanding the location and nature of Quaternary active crustal faults is critical to the reduction of both fault rupture and strong ground motions hazards in the built environment. Recent work along the San Ramon Fault in Santiago, Chile demonstrates that crustal seismic sources are important hazards. We present the results of a second likely Quaternary active fault (the El Arrayan Fault, EAF) that runs through the City of Santiago. The EAF was discovered at an outcrop in El Arrayan (Lo Barnechea) with up to the North reverse motion and sinistral (left-lateral) motion clearly visible and coincident with fault rocks (gouge, cataclasite, and breccia) and higher topography (i.e. uplift) in the hanging wall. The EAF is at least 12 km long, strikes North-Northwest to South-Southeast, and is steeply dipping (mean dip 77º NE). Clear geomorphic expression with sinistral displaced streams (up to ~210 m) suggest that this fault is Quaternary active and an important local source of fault rupture and crustal strong ground motions. Because no fault zone avoidance criteria in Chile, there is need for enhanced fault mapping, legislation, implementation of active fault rupture avoidance areas in Chile to reduce the risk posed by active crustal structures.

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Seismic risk analysis of concrete moment-resisting frames against near-fault earthquakes

Proceedings of the Institution of Mechanical Engineers Part O Journal of Risk and Reliability ◽

10.1177/1748006x20940472 ◽

2020 ◽

pp. 1748006X2094047

Author(s):

Ehsan Khojastehfar ◽

Farzad Mirzaei Aminian ◽

Hamid Ghanbari

Keyword(s):

Risk Analysis ◽

Seismic Risk ◽

Ground Motions ◽

Seismic Risk Analysis ◽

Strong Ground Motions ◽

Near Fault ◽

Moment Resisting Frames ◽

Short Period ◽

Moment Resisting ◽

Strong Ground

Characteristics of earthquake strong ground motions play an important role in the calculation of seismic-induced risk imposed on the structures. Distinguished features exist in movements recorded near seismic sources, as a result of a substantial amount of energy in a short period of record arrival time. In this article, seismic risk analysis of concrete moment-resisting frames due to near-fault strong ground motion is calculated and compared with that of caused by far-field strong ground motions. To achieve this goal, three moment-resisting frames with 4, 6, and 10 stories were designed based on international seismic design code. These frames are modeled applying modified Ibarra–Krawinkler moment–rotation nonlinear model in which strength and stiffness deterioration are involved. Seismic risk analysis of the frames is implemented using the Pacific Earthquake Engineering Research Center approach. Through this approach, probabilistic seismic hazard, probabilistic structural demand, probabilistic structural damage, and probabilistic loss curves are combined. Mean annual frequency of exceedance of seismic-induced losses presents probabilistic seismic risk of the sampled frames. According to the achieved results, the four-story frame (representative of low-rise frames) is more prone to be affected by near-fault strong ground motions in view of calculated seismic-induced risks.

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Seismic Behavior of MFPS Isolated Structure Under Near-Fault Sources and Strong Ground Motions With Long Predominant Periods

Seismic Engineering ◽

10.1115/pvp2003-2104 ◽

2003 ◽

Cited By ~ 12

Author(s):

C. S. Tsai ◽

Tsu-Cheng Chiang ◽

Bo-Jen Chen

Keyword(s):

Ground Motions ◽

Experimental Studies ◽

Shaking Table ◽

Well Performance ◽

Pendulum System ◽

Strong Ground Motions ◽

Near Fault ◽

Base Isolator ◽

Isolated Structures ◽

Strong Ground

Base isolation, which has been recognized as a very promising way for upgrading the earthquake-proof capability of existing structures both from theoretical and experimental studies. However, some researchers suspect the efficiency of base isolator under near-fault earthquakes and strong ground motions with long predominant periods. It is suggested from previous studies that earthquakes with long predominant periods always cause severe responses of base-isolated structures. In view of this, a new base isolator called as Multiple-Friction Pendulum System (MFPS) has been proposed in this study to improve the shortcoming of those undesirable phenomenon of base-isolated structures. In order to evaluate the efficiency of MFPS isolators, the shaking table tests of a 3-story steel structure have been performed at NCREE in Taiwan. Experimental results show that the proposed isolator still posses well performance under near source excitations and strong ground motions with long period predominant periods. Therefore, the proposed base isolator can be recognized as a very promising tool for enhancing the seismic-resistance of a structure near seismic faults or on a soft deposit soil.

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