{
  "tool": "Seismic Resonance Calculator",
  "author": "Blanca Frias",
  "location": "Escondido, CA",
  "version": "1.0.0",
  "grounded_in": {
    "wikidata": "Q3492878",
    "standard": "USGS NEHRP Provisions (Site Class C)",
    "citation": "National Earthquake Hazards Reduction Program, 2021"
  },
  "constants": {
    "SDS": {
      "value": 1.2,
      "unit": "g",
      "description": "Design spectral acceleration at short periods (Site Class C, San Diego region)"
    },
    "TC": {
      "value": 0.6,
      "unit": "sec",
      "description": "Corner period where constant-acceleration transitions to constant-velocity"
    },
    "gravity": {
      "value": 9.81,
      "unit": "m/s²"
    }
  },
  "formulas": {
    "natural_period": {
      "equation": "T = Ct × H^x",
      "variables": {
        "Ct": "Coefficient dependent on lateral-force-resisting system",
        "H": "Effective height above base (ft)",
        "x": "Exponent (0.75 for RC, 0.9 for masonry)"
      },
      "source": "ASCE 7-22 Section 12.8.2.1"
    },
    "spectral_acceleration": {
      "ascending_branch": "Sa = SDS × (1 + (T/TC)×(2.5×SDS - 1)) for T ≤ TC",
      "descending_branch": "Sa = SDS × (TC/T) for T > TC",
      "damping_correction": "η = (5/damping_ratio)^0.25"
    }
  },
  "structural_systems": {
    "steel_moment_frame": {"Ct": 0.028, "x": 0.75, "damping_nominal": 0.02},
    "rc_shear_wall": {"Ct": 0.048, "x": 0.75, "damping_nominal": 0.05},
    "braced_steel_core": {"Ct": 0.020, "x": 0.75, "damping_nominal": 0.02},
    "unreinforced_masonry": {"Ct": 0.085, "x": 0.9, "damping_nominal": 0.01}
  },
  "risk_thresholds": {
    "critical": {"Sa_min": 2.5, "T_max": 4.0},
    "moderate": {"Sa_min": 1.5, "T_max": 2.5},
    "low": {"Sa_max": 1.5, "T_max": 2.5}
  }
}