A Computational Tool for Ground-Motion Simulations Incorporating Regional Crustal Conditions

This article introduces a computational tool, namely ground-motion simulation system (GMSS), for generating synthetic accelerograms based on stochastic simulations. The distinctive feature of GMSS is that it has two independently developed upper-crustal models (expressed in the form of shear-wave velocity profiles), which have been built into the program for deriving the frequency-dependent crustal factors, and one of these models was originally developed by the authors. GMSS also has provisions to allow the user to specify their own preferred crustal profile. Sufficient details of both crustal models (forming part of the seismological model) and the accelerogram simulation methodology are presented herein in one article, to allow any person who has programming skills (on a user-friendly platform such as MATLAB, see Data and Resources), to develop their computational tools to implement any further innovations in crustal modeling for direct engineering applications. Crustal properties deep into bedrock can only be accounted for implicitly by conventional ground-motion prediction equation (GMPE) as much depends on the region where the ground motion was recorded. This limitation of existing GMPEs poses a challenge to engineering in regions that are not well represented by any strong-motion database. Toward the end of this article, readers are enlightened with the potential transdisciplinary utility of using GMSS, to facilitate the retrieval and scaling of accelerograms sourced from a database of real earthquake records through the construction of a conditional mean spectrum.

Selecting, scaling, and orienting three components of ground motions for intensity-based assessments at far-field sites

This article develops a methodology for selecting, scaling, and orienting three orthogonal components of ground motion (GM) when conducting intensity-based assessments of structures. Target spectra for selecting multicomponent GMs are critically examined and strategies for selecting hazard-consistent GMs are investigated. The Conditional Mean Spectrum–Uniform Hazard Spectrum (CMS-UHS) Composite Spectrum is proposed as an alternative to several Conditional Mean Spectra for selecting multicomponent GMs when conducting intensity-based assessments of complex three-dimensional (3D) structures. To ensure hazard consistency, multicomponent GMs should be selected using (a) the target spectrum for the vertical component of GM, (b) a wide range of vibration periods, and (c) scale factors that are constrained. With constrained scale factors, all three components of a GM can be reasonably scaled either by the same scale factor or by different scale factors.

Site Specific Response Analysis Kota Padang dari Input motion Conditional Mean Spectrum (CMS) Menggunakan Software NERA

Dalam perencanaan struktur bangunan tahan gempa, tujuan umum dari analisa struktur dinamis adalah memprediksi respons dari struktur terhadap pengaruh ground motion yang memiliki Spectral Acceleration (Sa) pada periode tertentu berdasarkan tingkat kemungkinan terlampui (Probability of Excedence/PE) 10% atau 2% masa layan bangunan 50 tahun. Prediksi respons struktur ditentukan dengan memilih ground motion yang cocok dengan beberapa target spektra dan nantinya ground motion tersebut digunakan sebagai input dalam analisis dinamis struktur. Pada paper ini menyajikan analisis perambatan gelombang gempa dari batuan dasar ke lapisan permukaan (Site Specific Response Analysis/ SSRA). Data-data yang diperlukan adalah data stratifikasi tanah dan parameter kecepatan gelombang geser yang didapatkan dari korelasi empiris terhadap data hasil pemboran dan uji N-SPT. Ground motion synthetic batuan dasar yang digunakan untuk perambatan gelombang gempa diperoleh dari hasil penelitian sebelumnya yang mengadopsi pendekatan statistik Conditional Mean Spectrum (CMS) agar ground motion yang dihasilkan dipermukaan cocok dengan prediksi masalah respon struktur yang sebenarnya. SSRA dilakukan berdasarkan teori perambatan gelombang geser satu dimensi dalam time domain dengan menggunakan program Non-linear Earthquake Response Analysis (NERA). Hasilnya diperoleh percepatan maksimum gempa dipermukaan (peak surface acceleration/ PBA) berbeda-beda di kedua lokasi tergantung pada faktor amplifikasi, karakteristik dan jenis gempa yang terjadi. Direkomendasikan respons spectra desain untuk periode ulang 475 tahun dan 2475 tahun wilayah 4 kelas tanah sedang (SD) untuk kedua lokasi tersebut. Data-data tersebut digunakan sebagai input dalam penentuan beban gempa pada bangunan dalam analisis struktur dinamis.