#
Kahramanmaraş—Gaziantep, Türkiye M_{w} 7.8 Earthquake on 6 February 2023: Strong Ground Motion and Building Response Estimations

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## Abstract

**:**

_{w}7.5 earthquake nine hours later, centered 95 km to the north–northeast from the first. Peak and cumulative seismic measures as well as elastic response spectra, constant ductility (or isoductile) response spectra, and incremental dynamic analysis curves were calculated for two representative earthquake records of the main event. Furthermore, the acceleration response spectra of a large set of records were compared to the acceleration design spectrum of the Turkish seismic code. Based on the study, it is concluded that the structures were overloaded far beyond their normal design levels. This, in combination with considerable vertical seismic components, was a contributing factor towards the collapse of many buildings in the region. Modifications of the Turkish seismic code are required so that higher spectral acceleration values can be prescribed, especially in earthquake-prone regions.

## 1. Introduction

_{w}) of 7.8 took place in Pazarcık, Kahramanmaraş, Türkiye at 04:17 a.m. local time (01:17 UTC) on 6 February 2023. The earthquake had a maximum Mercalli intensity of XI (Extreme) and it was followed by a M

_{w}7.5 earthquake nine hours later, centered 95 km to the north–northeast from the first. According to information available as of 22 February 2023, and a press release of the Turkish government [1], 42,310 people lost their lives in Kahramanmaraş, Gaziantep, Şanlıurfa, Diyarbakır, Adana, Adıyaman, Osmaniye, Hatay, Kilis, Malatya, and Elazığ, and 448,010 people have been evacuated from the earthquake zone. A total of 7184 aftershocks occurred, and a total of 5606 buildings have reportedly been destroyed in Türkiye [2]. In Türkiye and Syria combined, more than 6500 buildings have collapsed due to the two main shocks. As of 6 February 2023, a three-month state of emergency is in place in provinces directly affected by the earthquake in Türkiye [3]. The details of the earthquake event (from now on referred to as the M

_{w}7.8 event) are shown in Table 1 [4].

## 2. Literature Review

_{w}7.8) earthquake event which gave “collapse” results for the ground motion input of Station 3138. Following this, the earthquake ground motions were input to typical individual and urban buildings in Türkiye to assess the damage. Low- and high-rise reinforced concrete frame models were analyzed and subjected to the ground motion recorded at station 3123, and the results showed that there were large inter-story drifts at the lower stories in all cases, resulting in the collapse of all three frames analyzed.

_{w}7.8 earthquake on 6 February 2023. For example, in [25], kinematic rupture models from a joint inversion of High Rate Global Navigation Satellite System (HR-GNSS) and strong motion data sets of the two events in the 6 February 2023 Türkiye earthquake doublet have been developed, and it is shown that the M

_{w}7.8 earthquake nucleated on a previously unmapped fault before transitioning to the East Anatolian Fault (EAF), rupturing for ~350 km; the maximum rupture speeds were estimated to be 3.2 km/s for the same event. In another study [26], a long-period coda moment magnitude method was used to measure the moment magnitudes of the two large mainshocks. It was found that the magnitude of the first event (with one standard error of the magnitude estimation) is 7.95 ± 0.013. Results about the tectonic setting, the seismicity and its temporal evolution as well as the seismic moment release rate in the region have been presented in [27], whereas various issues about seismic forecasting are discussed in [28].

_{w}7.8 earthquake are calculated and assessed in an effort to provide some explanations about the large destructiveness of the earthquake and the devastating effects it had on buildings. A building-oriented evaluation of the earthquake impact is performed not only by extracting its various peak and cumulative parameters but also by calculating various types of linear and nonlinear (isoductile) seismic spectra. Furthermore, incremental dynamic analysis (IDA) [29] is performed for various simplified cases of buildings in an effort to estimate the response that they would exhibit during the earthquake. To the best of the authors’ knowledge, such a detailed investigation has not been conducted in the literature for the M

_{w}7.8 earthquake event. It is examined if the isoductile seismic spectra, the IDA curves, and the other calculated parameters can provide some hints about the destructiveness of the earthquake and how the buildings could be designed to be able to resist such earthquakes in the future. The objective of the study is to highlight various particular characteristics of the M

_{w}7.8 event through the investigation of all the aforementioned strong ground motion data processing results.

## 3. Record Data

_{w}7.8 earthquake event, one from each network: (i) Station No 3137, TK Network (Lat.: 36.69293°, Long.: 36.48852°) and (ii) KHMN Station, KO Network KO (Lat.: 37.3916°, Long.: 37.1574°); both are shown in Figure 1, together with the epicenter of the earthquake event. For the processing of the acceleration time histories, the open-source Matlab code OpenSeismoMatlab [30] was used, which has been developed by the authors and is quite reliable since it has been successfully verified in several cases in the literature [31,32,33]. The software uses an advanced time integration algorithm first presented in [34].

#### 3.1. Cumulative Energy, Arias Intensity, and Significant Duration Data

_{5–95}denotes the time needed for the 90% of the seismic energy to be released (5–95% interval), and td

_{5–75}denotes the time needed for the 70% of the seismic energy to be released (5–75% interval). These quantities are calculated using the following equations:

_{5}, td

_{75}, and td

_{95}the following conditions hold:

_{w}7.8 event was an event of large seismic power. This fact played a critical role in the intensity of the shaking that was experienced by structures and could provide some indirect hints explaining the large number of structural collapses. The aforementioned points become obvious by observing the normalized cumulative energy time histories shown in Figure 6 [35].

#### 3.2. Elastic Response Spectra

_{w}7.8 earthquake may provide an incentive for further improvements to the seismic codes in this direction [35].

#### 3.3. Isoductile response spectra

_{w}7.8 event is equal to 2.35 g as shown in Figure 9, whereas the corresponding value for the isoductile spectra is equal to 1.4 g as shown in Figure 14. The difference in the maximum spectral acceleration implies a substantial difference in the applied seismic forces, and this shows the importance of structural ductility. The collapses due to the M

_{w}7.8 earthquake showed in many cases a nonductile, brittle behavior, which in the case of reinforced concrete (RC) structures is closely related to under-reinforced structural elements. These structures, having limited ductility, responded in a more linear elastic-wise manner, and thus experienced much larger accelerations, which explains many of the building collapses [35].

#### 3.4. What Does the Turkish Seismic Code Provide?

_{w}7.8) considered in this study, can be taken into account.

#### 3.5. Does the High Spectral Acceleration in the Low Period Range Occur Only for the Two Examined Records or Is It a General Trend?

## 4. Structural Incremental Dynamic Analysis

#### 4.1. Spectral Acceleration–Ductility Curves

_{y}= 0.1 m in Figure 19a, or T = 1 s and u

_{y}= 0.1 m in Figure 19b). This is a common observation for structures responding in the elastoplastic regime. A general trend of the IDA curves is that with increasing intensity measure (spectral acceleration), the damage measure generally increases as well [35].

#### 4.2. Peak Ground Acceleration–Ductility Curves

_{y}= 0.01 m and T = 2 and u

_{y}= 0.1 m are nearly identical. This means that a stiff structure with low yield deformation can be equivalent to a flexible structure with moderate yield deformation. This has important implications for structural design. The latter type of structure is preferable since it is more economical. Therefore, reduced stiffness should be accompanied by moderate levels of yield deformation to ensure that a structure will be able to withstand high earthquake acceleration levels.

## 5. Distributions of Several Earthquake Characteristics

_{LN}and σ

_{LN}parameters of the lognormal distribution that appear in the legends of the histogram plots are different from the mean value and standard deviation of the data being plotted. The increased mean values of the plotted seismic parameters denote the increased impact of the 6 February 2023 Türkiye M

_{w}7.8 earthquake event.

_{w}7.8 earthquake event that occurred in Türkiye on 6 February 2023. For example, from Figure 5 of the work of Garini and Gazetas [46], where 99 recorded ground motions are selected to cover many of the well-known accelerograms from earthquakes of the last 30 years, and to include motions bearing near-fault characteristics (directivity and fling effects), it can be deduced that the Housner intensity values ranges roughly from 1 m to 6 m. In the study of Massumi and Gholami [47], a set of 85 far-field ground motion records from 17 earthquake events with moment magnitudes ranging from 5.9 to 7.6 and recorded for type II soil (Vs = 360–750 m/s) were processed. Figure 2 of this study shows the Housner spectral intensity ranging from 0 to 2.5 m. Since the range of the Housner intensities of the earthquake considered in this study is closer to that of [46], it is concluded that it can be highly possible that the earthquake considered in this study contains directivity and fling step phenomena, whereas it is confirmed that it was a severely strong event.

_{w}7.8 Türkiye earthquake are noted from Figure 28 to be equal to 6.29 m/s and 70 m/s, respectively. The fact that the average value falls into the middle of the aforementioned range shows the severity of the M

_{w}7.8 earthquake once again.

## 6. Conclusions

_{w}7.8 that hit the Kahramanmaraş–Gaziantep regions in southern Türkiye on 6 February 2023, was a rare event of extremely large seismic power; as shown in Section 3.1, where the total cumulative energy as well as its time history are calculated. This fact played a critical role in the intensity of the shaking that was experienced by structures and could provide some indirect hints explaining the large number of structural collapses. The acceleration spectral values of the seismic records that are calculated in Section 3.2 were found to be substantially larger than the design acceleration spectrum values according to the Turkish seismic code. Moreover, this difference between the design and the actual response spectra covered a large interval of periods, which includes the eigenperiods of most common buildings.

_{w}7.8 earthquake on SDOF structures can provide strong evidence that a relatively stiff structure with low yield deformation could be equivalent to a flexible structure with moderate yield deformation. This implies that reduced structural stiffness, which is the usual outcome of pursuing a more economical design, should be accompanied by moderate and not low levels of yield deformation to ensure that the structure will be able to withstand high earthquake acceleration levels. Under-reinforced concrete structures possess a low lateral stiffness combined with a low yield deformation, and this could explain the large number of collapses during the earthquake event when considering the much larger seismic damage imposed on SDOF systems with similar characteristics that are obvious in the various IDA curves presented in Section 4.

_{w}7.8 earthquake was indeed severely strong by comparing its various peak and cumulative seismic parameters to the corresponding seismic parameters of strong motion datasets from other major earthquakes in the past.

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Conflicts of Interest

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**Figure 1.**Locations of the two stations (No 3137 of TK Network and KHMN of KO Network) and the epicenter of the M

_{w}7.8 earthquake.

**Figure 2.**Earthquake acceleration time histories of the M

_{w}7.8 earthquake recorded at the TK.3137 station: (

**a**) east–west component, (

**b**) north–south component.

**Figure 3.**Earthquake acceleration time history of the M

_{w}7.8 earthquake recorded at the TK.3137 station: vertical component.

**Figure 4.**Earthquake acceleration time histories of the M

_{w}7.8 earthquake recorded at the KHMN Station: (

**a**) east–west component, (

**b**) north–south component.

**Figure 5.**Earthquake acceleration time histories of the M

_{w}7.8 earthquake recorded at the KHMN Station: vertical component.

**Figure 6.**Normalized cumulative energy that was released by the recorded M

_{w}7.8 earthquake, as recorded at the TK.3137 and the KO–KHMN stations: (

**a**) Horizontal components, (

**b**) Vertical components.

**Figure 7.**Spectral displacement (ζ = 5%) for the M

_{w}7.8 earthquake, as recorded at the TK.3137 and the KO–KHMN stations: (

**a**) horizontal components, (

**b**) vertical components.

**Figure 8.**Spectral velocity (ζ = 5%) for the M

_{w}7.8 earthquake, as recorded at the TK.3137 and the KO-KHMN stations: (

**a**) horizontal components, (

**b**) vertical components.

**Figure 9.**Spectral acceleration (ζ = 5%) for the M

_{w}7.8 earthquake, as recorded at the TK.3137 and the KO–KHMN stations: (

**a**) horizontal components, (

**b**) vertical components.

**Figure 10.**Spectral pseudo-acceleration (ζ = 5%) for the M

_{w}7.8 earthquake, as recorded at the TK.3137 and the KO–KHMN stations: (

**a**) horizontal components, (

**b**) vertical components.

**Figure 11.**Spectral pseudo-velocity (ζ = 5%) for the M

_{w}7.8 earthquake, as recorded at the TK.3137 and the KO–KHMN stations: (

**a**) horizontal components, (

**b**) vertical components.

**Figure 12.**Isoductile spectral displacement (ζ = 5%, μ = 2) for the M

_{w}7.8 earthquake, as recorded at the TK.3137 and the KO-KHMN stations: (

**a**) horizontal components, (

**b**) vertical components.

**Figure 13.**Isoductile spectral velocity (ζ = 5%, μ = 2) for the M

_{w}7.8 earthquake, as recorded at the TK.3137 and the KO–KHMN stations: (

**a**) horizontal components, (

**b**) vertical components.

**Figure 14.**Isoductile spectral acceleration (ζ = 5%, μ = 2) for the M

_{w}7.8 earthquake, as recorded at the TK.3137 and the KO–KHMN stations: (

**a**) horizontal components, (

**b**) vertical components.

**Figure 15.**Isoductile spectral pseudo-acceleration (ζ = 5%, μ = 2) for the M

_{w}7.8 earthquake, as recorded at the TK.3137 and the KO–KHMN stations: (

**a**) horizontal components, (

**b**) vertical components.

**Figure 16.**Isoductile spectral pseudo-velocity (ζ = 5%, μ = 2) for the M

_{w}7.8 earthquake, as recorded at the TK.3137 and the KO-KHMN stations: (

**a**) horizontal components, (

**b**) vertical components.

**Figure 17.**Design spectrum of the Turkish seismic code vs. actual acceleration response spectra for the M

_{w}7.8 earthquake (ζ = 5%), as recorded at TK.3137 and KO–KHMN stations: (

**a**) linear scale, (

**b**) logarithmic scale.

**Figure 18.**Design spectrum according to the Turkish seismic code vs. actual acceleration response spectra (ζ = 5%) of various records for the M

_{w}7.8 earthquake: (

**a**) linear scale, (

**b**) logarithmic scale.

**Figure 19.**IDA—spectral acceleration vs. ductility curves for the TK.3137 record and for various combinations of yield displacement (u

_{y}) and small strain eigenperiods (T) for the M

_{w}7.8 earthquake: (

**a**) EW component, (

**b**) NS component.

**Figure 20.**IDA—spectral acceleration vs. ductility curves for the KO–KHMN record and for various combinations of yield displacement (u

_{y}) and small strain eigenperiods (T) for the M

_{w}7.8 earthquake: (

**a**) EW component, (

**b**) NS component.

**Figure 21.**IDA—PGA vs. ductility curves for the TK.3137 record and for various combinations of yield displacement (u

_{y}) and small strain eigenperiods (T) for the M

_{w}7.8 earthquake: (

**a**) EW component, (

**b**) NS component.

**Figure 22.**IDA—PGA vs. ductility curves for the KO–KHMN record and for various combinations of yield displacement (u

_{y}) and small strain eigenperiods (T) for the M

_{w}7.8 earthquake: (

**a**) EW component, (

**b**) NS component.

**Figure 23.**Histogram plot of the PGA values of the various acceleration time histories of the M

_{w}7.8 earthquake and lognormal distribution fit.

**Figure 24.**Histogram plot of the EPGA values [45] of the various acceleration time histories of the M

_{w}7.8 earthquake and lognormal distribution fit.

**Figure 25.**Histogram plot of the PGV values of the various acceleration time histories of the M

_{w}7.8 earthquake and lognormal distribution fit.

**Figure 26.**Histogram plot of the spectral intensity according to Housner (1952) [43] of the various acceleration time histories of the M

_{w}7.8 earthquake and lognormal distribution fit.

**Figure 27.**Histogram plot of the spectral intensity according to Nau and Hall (1984) [44] of the various acceleration time histories of the M

_{w}7.8 earthquake and lognormal distribution fit.

**Figure 28.**Histogram plot of the Arias intensity of the various acceleration time histories of the M

_{w}7.8 earthquake and lognormal distribution fit.

**Figure 29.**Histogram plot of the significant duration (5–95%) of the various acceleration time histories of the M

_{w}7.8 earthquake and lognormal distribution fit.

Magnitude | 7.8 (M_{w}) |

Location | Pazarcık (Kahramanmaraş), 26 km ENE of Nurdağı, Türkiye |

Date and time | 6 February 2023, 01:17:34 UTC |

Latitude | 37.225° N |

Longitude | 37.021° E |

Depth | 10.0 km |

Station | TK.3137 | KO-KHMN | ||||
---|---|---|---|---|---|---|

Component | PGA (m/s ^{2}) | PGV (m/s) | PGD (m) | PGA (m/s ^{2}) | PGV (m/s) | PGD (m) |

EW Horizontal | 7.47 | 0.75 | 0.50 | 5.09 | 1.08 | 0.61 |

NS Horizontal | 4.26 | 0.76 | 1.15 | 6.06 | 0.89 | 0.50 |

UD Vertical | 4.46 | 0.40 | 0.16 | 4.79 | 0.45 | 0.34 |

Station | TK.3137 | KO-KHMN | ||||||
---|---|---|---|---|---|---|---|---|

Component | Ecum (m ^{2}/s^{3}) | td_{5–95}(s) | td_{5–75}(s) | Arias (m/s) | Ecum (m ^{2}/s^{3}) | td_{5–95}(s) | td_{5–75}(s) | Arias (m/s) |

EW Horizontal | 22.755 | 16.27 | 8.26 | 3.6 | 21.220 | 12.145 | 5.88 | 3.4 |

NS Horizontal | 22.232 | 16.79 | 9.58 | 3.6 | 28.743 | 10.28 | 4.64 | 4.6 |

UD Vertical | 13.932 | 16.68 | 9.71 | 2.2 | 13.731 | 16.59 | 5.44 | 2.2 |

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## Share and Cite

**MDPI and ACS Style**

Papazafeiropoulos, G.; Plevris, V.
Kahramanmaraş—Gaziantep, Türkiye M_{w} 7.8 Earthquake on 6 February 2023: Strong Ground Motion and Building Response Estimations. *Buildings* **2023**, *13*, 1194.
https://doi.org/10.3390/buildings13051194

**AMA Style**

Papazafeiropoulos G, Plevris V.
Kahramanmaraş—Gaziantep, Türkiye M_{w} 7.8 Earthquake on 6 February 2023: Strong Ground Motion and Building Response Estimations. *Buildings*. 2023; 13(5):1194.
https://doi.org/10.3390/buildings13051194

**Chicago/Turabian Style**

Papazafeiropoulos, George, and Vagelis Plevris.
2023. "Kahramanmaraş—Gaziantep, Türkiye M_{w} 7.8 Earthquake on 6 February 2023: Strong Ground Motion and Building Response Estimations" *Buildings* 13, no. 5: 1194.
https://doi.org/10.3390/buildings13051194