Overview

This repository provides six shapefile folders representing spatial decay-rate parameters for six ground-motion intensity measures across California:

• PGA (Peak Ground Acceleration)
• PGV (Peak Ground Velocity)
• PSA(0.1 s)
• PSA(0.3 s)
• PSA(1.0 s)
• PSA(3.0 s)

Each shapefile contains the posterior mean and posterior standard deviation of the spatial decay-rate parameter estimated for 322 grid cells (each 50 km × 50 km) covering California.

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File Naming Convention

Shapefile folders are named as:

CA_cells_50_xx

where xx indicates the corresponding intensity measure (e.g., pga, pgv, psa0p1, psa0p3, psa1, psa3).

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Data Description

Each shapefile’s attribute table includes eight columns:

Column Name	Description
id	Unique identifier for each 50 km × 50 km grid cell
left, top, right, bottom	Bounding coordinates (in WGS_1984_Web_Mercator projection)
lamb	Posterior mean of the spatial decay-rate parameter
lamb_sd	Posterior standard deviation of the spatial decay-rate parameter
cov	Coefficient of variation (lamb_sd / lamb)