The February 6th, 2023, Kahranmanmaras Earthquake sequence in Turkiye, HAEE, NTUA, TCG
Abstract
Following the devastating Kahramanmaraş earthquake sequence that took place on February 6th, 2023 in Turkyie, a joint reconnaissance mission was organized by the Technical Chamber of Greece (TCG / TEE), in collaboration with National Technical University of Athens (NTUA) and the Hellenic Association for Earthquake Engineering (HAEE / ETAM). This field work was organized in close collaboration with AFAD in Turkiye, and covered the cities of Pazarcik, Gaziantep, Gölbaşı, Adiyaman, Kahranmanmaras, Antakya, Iskenderun, Nurdağı, and Islahiye. The team assessed both geotechnical failures and structural damage and performed Rapid Visual Inspections for around 500 residential buildings.
In the Sivrice, Elazığ, Turkey earthquake on January 24, 2020, 41 people lost their lives, more than 1600 people were injured, 672 buildings collapsed, and around 12600 buildings were severely damaged due to poor construction quality. After such devastating earthquakes, damage assessment and forensic investigations are normally carried out quickly for a judicial process, and material qualities are revealed. However, emotional sensitivity of the victims in the earthquake affected zone and disruptions in key lifeline services such as transportation, electricity supply often make these processes difficult. After the Elazığ earthquake, along with the conventional in-situ core sampling method, concrete pieces were collected from columns of collapsed and severely damaged buildings and transported out of the earthquake zone to overcome these adverse conditions. Unlike in the conventional method where the whole sampling process is carried out in the earthquake zone, the core extraction from the transported concrete pieces was carried out outside the earthquake-affected area. The extracted concrete samples were checked for compliance with the prevailing material standards. Moreover, multiple reinforcing bars of various diameters were also extracted and tested to check their compliance with the standards. Besides, the results of examination of the quality of materials and workmanship used in the construction are also discussed, along with the precautions required to minimize fatalities and damage from similar buildings.
In this study, 525 reinforced concrete buildings which are determined as 'Risky Structure' within the scope of the Law on Transformation of Areas Under Disaster Risk in Hatay province, have been examined statistically. The structures examined according to the data of the Risky Building Detection Report Review Form prepared by the authorized companies; various types of data such as conveyor system type, construction year, reinforcement class, compressive strength are presented with graphics and evaluated statistically. The majority of the risky structures examined; it is determined that there are 1-2 storey buildings, between 1975-90 and they have 5-15 MPa compressive strength.
11 The Central Italy earthquake sequence initiated on 24 August 2016 with a moment 12 magnitude M6.1 event followed by a M5.9 and a M6.5 earthquake, that caused 13 significant damage and loss of life in the town of Amatrice and other nearby villages 14 and hamlets. The significance of this sequence led to a major international 15 reconnaissance effort to thoroughly examine the effects of this disaster. Specifically, 16 this paper presents evidences of strong local site effects (i.e., amplification of seismic 17 waves due to stratigraphic and topographic effects that leads to damage concentration in 18 certain areas). It also examines the damage patterns observed along the entire sequence 19 of events in association with the spatial distribution of ground motion intensity with 20 emphasis on the clearly distinct performance of reinforced concrete and masonry 21 structures under multiple excitations. The paper concludes with a critical assessment of 22
Turkey is located in a high seismicity region and has suffered extensive losses due to several major earthquakes that struck its various parts in the past two decades. While earthquakes are associated with damage and loss wherever they may occur, the destructive effects of those in Turkey are exacerbated by the large volume of code incompliant buildings constructed with poor materials and workmanship. As a large scale remedial initiative, Turkey has recently embarked upon a grand challenge of retrofitting or renewing all high-risk buildings within the next 20 years. This multi-million building and multi-billion dollar initiative has inevitably raised activity and debates in diverse disciplines regarding all aspects. This paper focuses on the methodologies and developing technologies for rapid condition assessment and structural evaluation of existing buildings in order to identify and prioritize high-risk buildings and for guiding decisions on retrofitting or renewal.
1] Could the directivity of a complex earthquake be inferred from the ruptured fault branches it created? Typically, branches develop in forward orientation, making acute angles relative to the propagation direction. Direct backward branching of the same style as the main rupture (e.g., both right lateral) is disallowed by the stress field at the rupture front. Here we propose another mechanism of backward branching. In that mechanism, rupture stops along one fault strand, radiates stress to a neighboring strand, nucleates there, and develops bilaterally, generating a backward branch. Such makes diagnosing directivity of a past earthquake difficult without detailed knowledge of the branching process. As a field example, in the Landers 1992 earthquake, rupture stopped at the northern end of the Kickapoo fault, jumped onto the Homestead Valley fault, and developed bilaterally there, NNW to continue the main rupture but also SSE for 4 km forming a backward branch. We develop theoretical principles underlying such rupture transitions, partly from elastostatic stress analysis, and then simulate the Landers example numerically using a two-dimensional elastodynamic boundary integral equation formulation incorporating slip-weakening rupture. This reproduces the proposed backward branching mechanism based on realistic if simplified fault geometries, prestress orientation corresponding to the region, standard lab friction values for peak strength, and fracture energies characteristic of the Landers event. We also show that the seismic S ratio controls the jumpable distance and that curving of a fault toward its compressional side, like locally along the southeastern Homestead Valley fault, induces near-tip increase of compressive normal stress that slows rupture propagation.
The Central Italy earthquake sequence nominally began on 24 August 2016 with aM6.1 event on a normal fault that produced devastating effects in the town of Amatrice and several nearby villages and hamlets. A major international response was undertaken to record the effects of this disaster, including surface faulting, ground motions, landslides, and damage patterns to structures. This work targeted the development of high-value case histories useful to future research. Subsequent events in October 2016 exacerbated the damage in previously affected areas and caused damage to new areas in the north, particularly the relatively large town of Norcia. Additional reconnaissance after a M6.5 event on 30 October 2016 documented and mapped several large landslide features and increased damage states for structures in villages and hamlets throughout the region. This paper provides an overview of the reconnaissance activities undertaken to document and map these and other effects, and highlights valuable lessons learned regarding faulting and ground motions, engineering effects, and emergency response to this disaster.
We develop a 2D slip-weakening description of a self-healing slip pulse that propagates dynamically in a steady-state configuration. The model is used to estimate patterns of off-fault secondary failure induced by the rupture, and also to infer fracture energies G for large earthquakes. This extends an analysis for a semi-infinite rupture (Poliakov et al., 2002) to the case of a finite slipping zone length L of the pulse. The dynamic stress drop, when divided by the drop from peak to residual strength, determines the ratio of L to the slip-weakening zone length R. Predicted off-fault damage is controlled by that scaled stress drop, static and dynamic friction coefficients, rupture velocity, principal prestress orientation, and poroelastic Skemp-ton coefficient. All damage zone lengths can be scaled by , which is proportional R* o G/(strength drop) 2 and is the value of R in the low-rupture-velocity, low-stress-drop, limit. In contrast to the Poliakov et al. (2002) case R/L 0, the region that supports Coulomb failure reaches a maximum size on the order of when mode II rupture R* o speed approaches the Rayleigh speed. Analysis of slip pulses documented by Heaton (1990) leads to estimates of G, each with a factor-of-two model uncertainty, from 0.1 to 9 MJ/m 2 (including the factor), averaging 2–4 MJ/m 2 ; G tends to increase with the amount of slip in the event. In most cases, secondary faulting should extend, at high rupture speeds, to distances from the principal fault surface on the order of 1 to 2 1–80 m for a 100-MPa strength drop; that distance should vary with depth, R* o being larger near the surface. We also discuss gouge and damage processes.
We study the stability of steady sliding between elastically deformable continua using rate and state dependent friction laws. That is done for both elastically identical and elastically dissimilar solids. The focus is on linearized response to perturbations of steady-state sliding, and on studying how the positive direct effect (instantaneous increase or decrease of shear strength in response to a respective instantaneous increase or decrease of slip rate) of those laws allows the existence of a quasi-static range of response to perturbations at sufficiently low slip rate. We discuss the physical basis of rate and state laws, including the likely basis for the direct effect in thermally activated processes allowing creep slippage at asperity contacts, and estimate activation parameters for quartzite and granite. Also, a class of rate and state laws suitable for variable normal stress is presented. As part of the work, we show that compromises from the rate and state framework for describing velocity-weakening friction lead to paradoxical results, like supersonic propagation of slip perturbations, or to ill-posedness, when applied to sliding between elastically deformable solids. The case of sliding between elastically dissimilar solids has the inherently destabilizing feature that spatially inhomogeneous slip leads to an alteration of normal stress, hence of frictional resistance. We show that the rate and state friction laws nevertheless lead to stability of response to sufficiently short wavelength perturbations, at very slow slip rates. Further, for slow sliding between dissimilar solids, we show that there is a critical amplitude of velocity-strengthening above which there is stability to perturbations of all wavelengths.
The aim of this article is to present a computer-aided comprehensive strategy for the rapid visual inspection of buildings and the optimal prioritization of strengthening and remedial actions that are necessary prior to, and after, a major earthquake event, respectively. Based on the visual screening procedures used in the United States and past experience in seismic assessment of buildings in Greece and Turkey (the two countries with the highest seismic risk in Europe), a building inventory is first compiled; then a vulnerability ranking procedure that is specifically tailored to the prevailing construction practice in Southeast Europe is implemented into a multi-functional, georeferenced computer tool, that accommodates the management, evaluation, processing and archiving of the data stock gathered during the pre- and post-earthquake assessment process, and the visualization of its spatial distribution. The methodology proposed and the computer system developed is then applied to the city of Düzce, Turkey, a city strongly damaged during the devastating 1999 earthquake.
- E Garini
- G Gazetas
Garini E., Gazetas G. (2023) "Preliminary Report on the M7.8 and M7.5 earthquakes of February 6,
2023 in Turkey-Syria, DOI 10.17605/OSF.IO/V4MSW