none 10.1177/87552930231203989 Wiley Wiley (John Wiley & Sons) 311 154111964 5867 2026012503564800433 10.1002 2026-01-25T12:23:35Z 2023-10-19T06:53:16Z 16 Earthquake Spectra Earthquake Spectra 8755-2930 1944-8201 02 2024 40 1 Nathan Girmay Department of Civil & Environmental Engineering Stanford University Stanford CA USA https://orcid.org/0009-0007-3597-4154 Alan Poulos Department of Civil & Environmental Engineering Stanford University Stanford CA USA https://orcid.org/0000-0001-8654-1024 Eduardo Miranda Department of Civil & Environmental Engineering Stanford University Stanford CA USA https://orcid.org/0000-0001-9398-443X Until recently, the orientation of maximum horizontal spectral response was generally believed to not have a predominant orientation at rupture distances greater than 5 km. However, a recent study found that the orientation of maximum spectral response for strike‐slip earthquakes in the NGA‐West2 database tends to occur close to the epicentral transverse orientation, that is, an orientation perpendicular to a line connecting the epicenter to the station. This article investigates directionality in the 6 February 2023 Türkiye doublet earthquakes ( M w 7.8 and 7.5) with strike‐slip faulting. The orientation of the maximum response of 5%‐damped linear elastic oscillators was studied. The spatial distribution of the level of polarization, which in this article refers to the amount of directionality, and intensities at specific orientations were also studied. The maximum spectral response was found to occur systematically close to the epicentral transverse orientation, consistent with previous observations for other strike‐slip earthquakes. For the M w 7.8 event where the location of maximum slip was relatively far from the epicenter, it was found that the orientation of maximum spectral response is, on average, closer to the maximum slip transverse orientation (i.e. perpendicular to a line connecting the station to the surface projection of the point of maximum slip) when compared to the epicentral transverse orientation over most period ranges. This suggests that the maximum slip transverse orientation may be a better estimator for determining the orientation of maximum spectral response in large‐magnitude strike‐slip earthquakes, although further study using more events is warranted. Polarized motions were observed over large geographical areas, and the orientation of maximum spectral response was found to be close to the epicentral or maximum slip transverse for Joyner–Boore distances up to the farthest studied (400 km). These findings further support the case for the development of orientation‐dependent ground motion models for strike‐slip earthquakes. 02 2024 02 2024 486 504 10.1177/87552930231203989 John A. Blume Earthquake Engineering Center, Stanford University https://doi.org/10.13039/100019658 John A. Blume Fellowship Stanford University https://doi.org/10.13039/100005492 Nancy Grant Chamberlain Fellowship http://onlinelibrary.wiley.com/termsAndConditions#vor http://doi.wiley.com/10.1002/tdm_license_1.1 2 10.1177/sage-journals-update-policy journals.sagepub.com true John A. Blume Earthquake Engineering Center, Stanford University https://doi.org/10.13039/100019658 John A. Blume Fellowship Stanford University https://doi.org/10.13039/100005492 Nancy Grant Chamberlain Fellowship National Agency for Research and Development (ANID) / Doctorado Becas Chile 2019-72200307 https://journals.sagepub.com/page/policies/text-and-data-mining-license 10.1177/87552930231203989 https://onlinelibrary.wiley.com/doi/10.1177/87552930231203989 http://sage.cnpereading.com/paragraph/article/?doi=10.1177/87552930231203989 https://onlinelibrary.wiley.com/doi/pdf/10.1177/87552930231203989 https://onlinelibrary.wiley.com/doi/pdf/10.1177/87552930231203989 https://onlinelibrary.wiley.com/doi/full-xml/10.1177/87552930231203989 https://pubs.geoscienceworld.org/earthquake-spectra/article/40/1/486/633866/directionality-and-polarization-of-response 10.1785/gssrl.68.1.94 AFAD Turkish Disaster and Emergency Management Presidency (AFAD)(2023a)06.02.2023 01:17:32 Pazarcık (Kahramanmaraş) earthquake MW 7.7. Available at:https://tadas.afad.gov.tr/event‐detail/17966(accessed April 2023). AFAD Turkish Disaster and Emergency Management Presidency (AFAD)(2023b)06.02.2023 10:24:47 Elbistan (Kahramanmaraş) earthquake MW 7.6. Available at:https://tadas.afad.gov.tr/event‐detail/17969(accessed April 2023). 10.1007/s10950-009-9176-9 Minimum Design Loads for Buildings and Other Structures (ASCE/SEI 7‐16) American Society of Civil Engineers (ASCE) 2016 Minimum Design Loads for Buildings and Other Structures (ASCE/SEI 7‐16) American Society of Civil Engineers (ASCE) 2022 10.1193/070913EQS197M 10.1785/0120050210 BooreDM(2004)Choosing the lowest usable frequency for response spectra from filtered data. Available at:http://www.daveboore.com/daves_notes/lowest_usable_freq_for_response_spectra_v20.pdf(accessed April 2023). 10.1785/0120090400 10.1785/0120160250 10.1785/gssrl.68.1.128 10.1193/070113EQS184M 10.1785/0120050209 Earthquake Engineering Research Institute (EERI) and Geotechnical Extreme Event Reconnaissance Association (GEER)(2023)February 6 2023 Türkiye earthquakes: Report on geoscience and engineering impacts. Available at:https://learningfromearthquakes.org/images/2023_02_06_nurdagi_turkey/GEER_2023_Turkey_Earthquake_FullReport_ReducedSize.pdf(accessed 7 May 2023). 10.1007/s10518-016-0041-2 10.1785/0120060194 10.1193/1.2830435 10.3133/ofr82881 JoynerWB BooreDM(1982)Estimation of response‐spectral values as functions of magnitude distance and site conditions. Open‐file report United States Geological Survey Reston VA 1 January. 10.1214/aoms/1177729694 10.1785/0120040111 Selecting and scaling earthquake ground motions for performing response‐history analysis. Technical report NIST GCR 11‐917‐15, November NEHRP Consultants Joint Venture 2011 10.1007/978-94-007-0152-6_8 10.1002/eqe.3654 10.1785/0120230001 10.1193/040913EQS097M 10.1785/gssrl.68.1.199 United States Geological Survey (USGS)(2023a)M 7.5—Elbistan earthquake Kahramanmaras earthquake sequence (Event page). Available at:https://earthquake.usgs.gov/earthquakes/eventpage/us6000jlqa/executive(accessed 13 April 2023). United States Geological Survey (USGS)(2023b)M 7.8—Pazarcik earthquake Kahramanmaras earthquake sequence (Event page). Available at:https://earthquake.usgs.gov/earthquakes/eventpage/us6000jllz/executive(accessed 13 April 2023).