地震シミュレーションソフトウェア: エンジニアリングツール

The Role of Simulation in Earthquake Engineering

Earthquake simulation software enables engineers, researchers, and risk analysts to answer questions that cannot be answered through physical experimentation alone: How will an unbuilt structure perform in a once-in-500-years earthquake? What is the expected annual loss to a portfolio of 10,000 buildings distributed across a seismically active region? What ground motions should be used to design a dam in a region with incomplete historical records? The answers to these questions emerge from computational models that integrate seismological source models, wave propagation physics, soil-structure interaction, and structural dynamics into a unified analytical framework.

Finite Element Structural Analysis

At the building scale, nonlinear finite element analysis (FEA) is the primary tool for earthquake response simulation. Software packages including OpenSees (open-source, UC Berkeley), PERFORM-3D (Computers and Structures), SAP2000 Nonlinear, ABAQUS, and LS-DYNA represent the structural system as a mesh of elements with specified material constitutive laws. For earthquake analysis, elements must be capable of capturing nonlinear hysteretic behavior — the yielding, degrading, and re-stiffening that structural members undergo during cyclic inelastic deformation. The accuracy of simulation results depends critically on the calibration of material models against experimental test data from structural component tests.

Ground Motion Simulation

確率論的地震ハザード解析（PSHA）起こりうるすべての地震の発生源・マグニチュード・地震動レベルを考慮し、特定の揺れの水準を超える確率として結果を表現する、地震ハザードの定量評価手法。 requires ground motion prediction equations (GMPEs) to estimate shaking at sites, but complex site-specific assessments benefit from physics-based ground motion simulation. Stochastic simulation methods (stochastic finite fault models) represent the earthquake source as a sum of many small sub-faults radiating stochastic ground motion consistent with seismological scaling relations. Deterministic methods (finite difference and spectral element codes like Hercules, SW4, and Specfem3D) solve the three-dimensional elastic wave equation on computational grids, capturing the effects of basin geometry, velocity structure, and 断層線地表に現れた断層の痕跡で、線状または破砕された岩石の帯として視認できる。地質学者は活断層線を地図化し、周辺地域の地震リスクを評価する。 geometry on ground motion amplification and focusing. The vulnerability functions特定の建物タイプについて、揺れの水準に応じたさまざまな被害段階の発生確率を示す数学的関数。損失推定モデルに不可欠な要素。 used in regional loss estimation are derived from simulated ground motions applied to large suites of structural models.

Regional Loss Estimation: HAZUS and OpenQuake

For regional 損失推定想定される地震シナリオから経済的損失や死傷者数を予測する過程。FEMAのHAZUSソフトウェアは、アメリカにおける標準的な損失推定ツールである。, simulation shifts from individual structures to large portfolios. FEMA's HAZUS software performs loss estimation by combining シェイクマップ（ShakeMap）地震発生後の揺れの強さの分布を示すUSGSの成果物。地震計データ、地震動モデル、「揺れを感じましたか？」の報告を組み合わせて作成される。 or 確率論的地震ハザード解析（PSHA）起こりうるすべての地震の発生源・マグニチュード・地震動レベルを考慮し、特定の揺れの水準を超える確率として結果を表現する、地震ハザードの定量評価手法。 ground motion with a building inventory database and vulnerability functions特定の建物タイプについて、揺れの水準に応じたさまざまな被害段階の発生確率を示す数学的関数。損失推定モデルに不可欠な要素。 that relate shaking intensity to damage state probabilities. Output includes estimates of casualties, displaced households, dollar losses, and infrastructure damage by census tract or county. HAZUS uses fragility functions derived from engineering judgment, laboratory testing, and post-earthquake building survey data. Fragility functions express the conditional probability of reaching or exceeding a specific damage state (none, slight, moderate, extensive, complete) given a specified shaking intensity.

The GEM OpenQuake Platform

OpenQuake Engine, the GEM Foundation's open-source loss estimation platform, extends HAZUS-style approaches with more flexible input options, probabilistic source characterization, and open exposure databases (GED4ALL global exposure model). OpenQuake can perform scenario-based loss calculations (for specified earthquake scenarios), classical PSHA-based probabilistic loss calculations, and event-set calculations using stochastic event catalogs. The platform supports 地震リスク評価特定の地域や構造物について、地震ハザード・建物の脆弱性・想定される損失を評価する過程。ハザードマップ、建物台帳、被害モデルを組み合わせて行われる。 at national to global scales and has been used to produce the Global Seismic Risk Map published by GEM.

Soil-Structure Interaction Simulation

The interaction between a building foundation and the surrounding soil modifies both the ground motion input to the structure and the structural response. Soil-structure interaction (SSI) simulation uses finite element or boundary element methods to model the soil domain surrounding the foundation, capturing effects like foundation embedment, soil compliance, and kinematic interaction (the inability of a rigid foundation to perfectly follow the free-field ground motion). SSI effects can be beneficial — reducing structural demands through foundation rocking — or detrimental — amplifying shaking in soft soils through 地盤増幅（サイト効果）軟弱な土壌や堆積層が地震波を増幅させることによって生じる、揺れの強さの増大。軟弱地盤上の構造物は、基盤岩上の構造物に比べて2〜10倍強い揺れを経験することがある。 and 構造物の共振地震波の周波数が建物の固有振動数と一致したときに生じる、建物の揺れの増幅現象。低層建物は高周波数の波と、高層建物は低周波数の波と共振しやすい。 effects.

Shake Table Physical Testing and Model Calibration

Simulation software must be validated against experimental data to be trustworthy. Shake table testing subjects physical structural models to earthquake ground motion recordings, generating measured response data that validates analytical models. Major shake table facilities include the NEES/NHERI E-Defense facility in Japan (the world's largest 3D shake table, capable of testing full-scale structures) and the facilities at UC San Diego, Lehigh University, and the University of Buffalo. Blind prediction contests, where analysts submit structural response predictions before the shake table test is run, rigorously evaluate simulation accuracy and reveal systematic model biases.

Monte Carlo Methods in Earthquake Risk

Regional 損失推定想定される地震シナリオから経済的損失や死傷者数を予測する過程。FEMAのHAZUSソフトウェアは、アメリカにおける標準的な損失推定ツールである。 for insurance and financial risk management employs Monte Carlo simulation to characterize loss distributions. A stochastic event catalog is generated containing thousands of simulated years of earthquake activity, sampling from the 確率論的地震ハザード解析（PSHA）起こりうるすべての地震の発生源・マグニチュード・地震動レベルを考慮し、特定の揺れの水準を超える確率として結果を表現する、地震ハザードの定量評価手法。 source model and グーテンベルク・リヒター則地震の頻度とマグニチュードの関係を示す統計法則で、マグニチュードが1単位増えるごとに、地震の発生頻度はおよそ10分の1になる。 magnitude-frequency relationships. Each catalog event is combined with a ground motion simulation and a building damage model to produce a loss for that event. Aggregating over many thousands of events and catalog years produces exceedance probability curves for annual, aggregate, and occurrence losses — the basis for catastrophe insurance pricing and 予想最大損失額（PML）単一の地震事象によって、保険ポートフォリオや不動産が被る可能性のある最大損失額の推定値。保険会社・再保険会社にとって重要な指標。 calculations used in property financing.

High-Performance Computing Requirements

The most detailed earthquake simulations — physics-based ground motion simulation at regional scale with spatial resolution sufficient to capture basin effects — require high-performance computing (HPC) resources. Simulations of the 1994 Northridge and 1906 San Francisco earthquakes using Specfem3D have run on tens of thousands of processor cores simultaneously. As computational resources grow, simulation resolution improves, enabling direct coupling of seismic source physics, wave propagation, soil response, and structural analysis in a single integrated simulation — a long-term research goal that would dramatically improve earthquake risk assessment accuracy.

Summary

Earthquake simulation software spans scales from individual structural elements to entire building inventories across regional loss models. The 確率論的地震ハザード解析（PSHA）起こりうるすべての地震の発生源・マグニチュード・地震動レベルを考慮し、特定の揺れの水準を超える確率として結果を表現する、地震ハザードの定量評価手法。 framework provides the probabilistic ground motion input; finite element codes simulate structural response; OpenQuake and HAZUS aggregate vulnerability functions特定の建物タイプについて、揺れの水準に応じたさまざまな被害段階の発生確率を示す数学的関数。損失推定モデルに不可欠な要素。 with exposure to produce 損失推定想定される地震シナリオから経済的損失や死傷者数を予測する過程。FEMAのHAZUSソフトウェアは、アメリカにおける標準的な損失推定ツールである。 products. These tools collectively enable quantitative earthquake risk management that would be impossible through purely empirical or judgment-based approaches.