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📖 Introduction

ECAT is a unified framework for adaptive fault modeling and earthquake cycle analysis. It integrates fault constructing, forward modeling, data processing, and advanced inversion strategies into a comprehensive toolkit.

Key Goals:

• Provide robust tools for the entire Forward and Inverse earthquake cycle.
• Support complex fault geometries with adaptive meshing.
• Enable flexible hyperparameter estimation strategies (Single, Individual, Grouped).
• Continuous Updates: Stable features are integrated regularly, with ongoing bug fixes and new module additions.

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💻 Installation

See Install.md for detailed instructions.

Quick Start

# Clone the repository
git clone [https://github.com/kefuhe/ECAT.git](https://github.com/kefuhe/ECAT.git)
cd ECAT
# Run installation script
./install.sh  # Linux/Mac
# or install.bat for Windows

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🏃 Running ECAT & Case Studies

ECAT relies on a rich library of cases for testing and research. To run ECAT effectively, you should first obtain the case library.

3.1 Get the Case Library (Basic Running)

The full case library is hosted in a separate repository (ECAT-Cases). You have two options to download it:

Option 1: Auto-download via Install Script Uncomment the following line in install.sh / install.bat before running installation:

git submodule update --init --recursive

Option 2: Manual Download

# Using the helper script
./download_cases.sh

# Or direct clone into the directory
git clone [https://github.com/kefuhe/ECAT-cases.git](https://github.com/kefuhe/ECAT-cases.git)

3.2 Method & Example Modules

Basic examples to understand specific modules of ECAT.

🏷️ Category	⚡ Earthquake Example	📝 Description (Date, Magnitude, Type)	📁 Directory (in ECAT-Cases)
Downsampling	InSAR Downsampling	Example code for InSAR downsampling	Details
Nonlinear Inversion	Hotan Earthquake	2020-06-25, Mw6.3, Normal	Details
	Iran Earthquake	2017-04-05, Mw6.1, Reverse	Details
	Taiwan Earthquake	2024-04-05, Mw7.4, Reverse	Details
	Wushi Earthquake	2024-01-22, Mw7.0, Strike-slip	Details
	Western Xizang	2020-07-22, Mw6.3, Normal	Details
BLSE Linear Inversion	Dingri Earthquake 2020	2020-03-20, Mw5.7, Normal	Details

3.3 Real Earthquake Case Studies (Visual Gallery)

Advanced applications demonstrating adaptive fault geometry and complex slip distribution.

A. Adaptive Fault Geometry with Relocated Aftershocks

Case 1: 2021 Maduo Earthquake (Mw 7.4)

Case 2: 2023 Kahramanmaraş Türkiye Doublet

Complex multi-segment modeling with variance dip angles.

Case 3: 2022 Luding Earthquake

Pre-Clustering Selection Followed by Fitting.

B. Isocurve Fitting (Depth-focused Aftershocks)

Note: Robust curve fitting serves as a reference. Final curves often incorporate user interaction.

C. Comprehensive Research Cases List

🌏 Case Name	📝 Description	🔗 Link
Dingri 2015	2015-04-25, Mw5.7, Normal	Details
Dingri 2020	2020-03-20, Mw5.6, Normal	Details
Dingri 2025	2025-01-07, Mw7.0, Normal	Details
Sagaing 2025	2025-03-28, Mw7.8, Strike-slip	Details

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🚀 Core Features & Workflow

1. Inversion Workflow & Strategies

ECAT supports a flexible inversion pipeline, ranging from standard step-wise inversion to advanced joint Bayesian optimization.

• Data Processing:
  • InSAR/Offset: Supports Resolution-based (fault-dependent) and Quadtree-based (fault-independent) downsampling.
  • GNSS: Direct integration without downsampling.
• Inversion Strategies:
  • Standard Two-Step: Nonlinear geometry search followed by Linear slip inversion (BLSE/VCE).
  • SMC-FJ (Joint Strategy): Simultaneous estimation of Geometry + Slip + Hyperparameters using Bayesian optimization.
• Hyperparameter Modes (Unique Feature): For both Linear (BLSE; VCE) and Bayesian parts, data weights and smoothing factors can be estimated in three modes:
  • Single: Global factor for all datasets/faults (Default for smoothing).
  • Individual (Default): Independent factor for each dataset/fault-segment (Default for weighting).
  • Grouped: Cluster-based factors for user-defined groups.

2. Adaptive Fault Construction & Meshing

ECAT offers versatile methods to build complex fault geometries from various data sources.

• Construction Modes:
  1. Planar: Simple geometry from GCMT or nonlinear inversion results.
  2. Listric: Depth-dependent dip (exponential decay/SDM-style).
  3. Trace + Profile: Lofted surfaces defined by surface traces and variable dip profiles.
  4. Contour: 3D surfaces from Slab2.0 depth contours or iso-depth curves.
• Meshing:
  • Triangular Elements (T3): Recommended for complex, gap-free surfaces.
  • Rectangular Elements (Q4): Supported for simple planar geometries.

3. Forward Modeling Engines

ECAT utilizes layered Green's function calculations powered by edcmp and pscmp, supporting both rectangular and triangular elements.

For details, see README in the csi subdirectory.

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🚧 Modules in Development

Postseismic (Beta)

• Engine: pscmp_visco_postseismic.py
• Features: Combined model of viscoelastic relaxation and stress-driven afterslip.
  • cv_cum: Viscoelastic relaxation due to coseismic slip.
  • as_cum: Afterslip calculation.
  • calAS_AV: Viscoelastic relaxation due to afterslip.

Interseismic (Alpha)

• Engine: pscmp_visco_interseismic.py
• Function: calviscoGfromPscmp for earthquake cycle velocity calculations.

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📝 Citation

If you use ECAT in your research, please cite:

He K., C. Xu, Y. Wen, Y. Zhao, G. Xu, L. Sun, and J. Wang (2025). A Unified Framework for Adaptive Fault Modeling: Methods and Applications. SCIENCE CHINA Earth Sciences . DOI: 10.1007/s11430-025-1773-0.

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