Journal of Seismology and Earthquake Engineering
Year:2024 | Volume:26 | Issue:2|Papers Count:6

Sarpol-e Zahab, in the west of Iran, is subjected to a high earthquake risk. Located in the north part of the Zagros seismic belt and is surrounded by several active faults that show some M7+ earthquake records.Nowcasting refers to the process of determining the uncertain state of the seismicity at the present time by indirect means for the seismically active regions, where the goal is to estimate the current state of risk, the current state of the fault system, and its current level of progress through the earthquake cycle. The local catalog of earthquakes is used, using “small” earthquakes to determine the level of hazard from “large” earthquakes in the region. To evaluate the statistical distribution of the inter-event counts of small events that occur between large events, the natural time concept was used rather than clock time (Origin Time of Earthquake). This method does not involve any model other than the idea of an earthquake cycle. Rather, a specific radius and a specific large earthquake magnitude of interest is defined, ensuring that we have enough data to span at least ~10 or larger earthquake cycles in the region. We then compute the earthquake potential score (EPS) which is defined as the cumulative probability distribution P (nn(t) for the small earthquakes in the region. The EPS was calculated as the total number of small earthquakes after the last large occurrence in the studied area. EPS is therefore the current level of hazard and assigns a number between 0% and 100% to every region so defined, thus providing a unique measure. Physically, the EPS corresponds to an estimate of the level of progress through the earthquake cycle in the defined region at the current time.We have determined the EPS values to consider events of Mw≥4.4 within two different radiuses (250 and 350 km) around Sarpol-e Zahab. The EPS values for Sarpol-e Zahab at 250 km corresponding to Mw≥5.5 and six events were found to be almost 0.86 and 0.97, respectively, while at 350 km these values are equal to 0.73 and 0.50 for Mw≥5.5 and six events, respectively.

This paper presents a novel rocking system for bridge piers that aims to minimize structural damage and reduce residual drift during seismic events. This system relies on gravity for re-centering and does not utilize post-tensioned tendons. It consists of a pair of tubular steel columns attached to the foundation and cap beam with rocking connections. Each connection utilizes a friction damper that absorbs energy through friction at low lateral displacement and plastic deformation at large lateral displacement. Finite element (FE) simulation was utilized to evaluate the behavior of this system under vertical and lateral loading. The finite element models under two different gravity loads were subjected to lateral cyclic loading to study the re-centering characteristics of the system. The analyses have demonstrated that the system exhibits a flag-shaped hysteresis response with minimal residual drift. A supplementary analysis has also shown that any residual drift in this system can be recovered by loosening bolts in the frictional connection.

Empirical studies have demonstrated a significant interaction between nonlinear flexural and shear responses in reinforced concrete shear walls. This paper investigates the implications of shear-flexural interaction (SFI) on the seismic performance of high-rise reinforced concrete dual frame-wall systems. Structures with three different heights (20, 25 and 30 stories) are analyzed. Comparative structural analyses are conducted using two modeling approaches for shear walls: one incorporating SFI and the other neglecting it. A set of ground motion records from the Federal Emergency Management Agency (FEMA) P695 is utilized to perform incremental dynamic analysis, facilitating a detailed evaluation of structural behavior under seismic loading. Collapse risk assessment encompasses seismic hazard analysis and the determination of collapse fragility. Furthermore, the collapse performance is appraised following the FEMA P695 methodology. The results underscore the substantial impact of SFI on both seismic performance and collapse risk in high-rise reinforced concrete structures. Specifically, integrating SFI into shear wall modeling results in elevated collapse risk and diminished ACMR. This underscores the pivotal role of SFI in shaping structural resilience.

Two devastating earthquakes struck on February 6, 2023, the first with a magnitude of 7.7 at 04:17 in the Pazarcık district of Kahramanmaraş, and the second one with a magnitude of 7.6 at 13:24 in the Ekinözü and Elbistan districts of Kahramanmaraş in eastern and southeastern Anatolia, as well as northern Syria. These two earthquakes caused vast destruction in 11 provinces and affected 15.2 million people, including 5.4 million children, living in stricken provinces (Kahramannaras and Hatay Report, Post Earthquake Assessment, 2023). The two earthquakes had a devastating impact on settlements, housing, and businesses in most of the impacted locations, with extremely high levels of damage in highly populated areas. The Nirengi, a Turkish Non-governmental Organization team's reflections on the severe impact of the two earthquakes and living conditions in several lifeline sectors, derived through field observations, data from interviewees, and partly desk research, which are presented briefly in this paper. The provided information has been gathered a few days after the earthquake and the recommendations are noted based on the findings of initial assessment following the disaster. Also results of the observations one year after the earthquake are presented to show the trend and progress in aiding the affected people.

This paper investigates the effect of the soil type on the torsional response of buildings experiencing torsional pounding due to earthquake excitations. Six buildings (one 4-storey building and five 6-storey buildings) with different configurations have been considered. First, pounding between different structures has been analysed for a specified soil type and the effect of the torsional pounding and the contact asymmetry on the torsional response of colliding buildings has been investigated. Then, these pounding cases have been considered for different soil types to study the effect of the soil type on the torsional response of buildings experiencing torsional pounding. Five soil types have been considered, i.e. hard rock, rock, very dense soil and soft rock, stiff soil and soft clay soil. The results of the study indicate that the earthquake-induced torsional pounding causes an increase in the peak storey rotation of the colliding buildings as compared to the symmetric pounding in all cases. Higher peak storey rotations have been experienced for colliding buildings founded on the soft clay soil, then for buildings founded on the stiff soil, then for buildings founded on very dense soil and soft rock, and finally for buildings founded on the rock and hard rock.

This paper considering two buildings different in height as a case study to inquiries into the effect of recorded and spectrally matched ground motions (simulated ground motion). Model of structures are developed using design procedure of Chapter 12 of ASCE 7-22 and linear analysis is adopted using requirements of Chapter 16 of ASCE 7-22. In this study, the effects of recorded and simulated ground motions on drift distribution and also floor acceleration are investigated.  It could be seen that all of the structures, when subjected to simulated ground motions, give acceptable performance, even though this is not the case with amplitude-scaled ground motions.