Abstract
Earthquake detection systems require robust discrimination between seismic
signals and noise to mitigate risks and enable timely responses. Traditional methods, such
as the Short-Term Average/Long-Term Average (STA/LTA) algorithms and
deterministic machine learning models, often struggle with noisy data and fail to quantify
uncertainty in their output—a critical gap for high-stakes decision-making. This thesis
proposes a Bayesian Convolutional Neural Network (BCNN) framework that advances
seismic signal classification, specifically, the binary discrimination of earthquake signals
from noise waveforms by integrating uncertainty quantification. The proposed
framework models both epistemic and aleatoric uncertainties. Epistemic uncertainty
stems from limited or unrepresentative training data and can be reduced with additional
data. Conversely, aleatoric uncertainty captures the inherent variability in data, such as
low signal-to-noise ratios (SNR), overlapping features between earthquake and noise
waveforms, and complex wave propagation effects; and is irreducible. By quantifying
these uncertainties, the BCNN framework identifies low-confidence predictions, enabling
more reliable decision-making in earthquake early warning and monitoring systems.
A preliminary comparative study evaluated three architectures, namely, Fully
Connected Neural Networks (FCNN), Recurrent Neural Networks (RNN), and
Convolutional Neural Networks (CNN) on the Southern California Earthquake Data
Center (SCEDC) dataset, achieving validation accuracies of 94.7%, 96.0%, and 99.3%,
respectively. Given CNNs superiority in capturing spatiotemporal patterns, it was
selected as the foundation for the Bayesian framework. Leveraging Flipout layers and
variational inference, the BCNN models uncertainty, providing confidence estimates
alongside classifications. Trained on the Southern California Earthquake Data Center
(SCEDC) dataset, the model achieves 99.1% accuracy, while identifying ambiguous cases
through entropy-based metrics. Comparative analyses reveal its superiority over
deterministic CNNs, particularly for low SNR and complex waveform variability.
The framework is evaluated across diverse tectonic settings, including Himalayan
earthquakes and near-/far-fault waveforms. While it maintains strong performance for
data resembling its training distribution (e.g., near-fault signals), its accuracy declines for
geologically distinct regions (63.3% for Himalayan events, 68.4% for near-fault and 86.7%
for far-fault), highlighting the need of region-specific training. Uncertainty estimates
correlate with classification errors, enabling proactive flagging of low-confidence signals
for human review. This work offers a scalable, interpretable tool for disaster risk
reduction. The BCNN’s probabilistic outputs not only enhance reliability but also align
with ethical AI principles, ensuring transparency in life-critical applications.