Amplitude Threshold Earthquake Detection

Traditional amplitude-based detection method: simple but with significant limitations compared to matched filtering

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Missed Events

Simple Amplitude Threshold Detection

The most basic earthquake detection method triggers when the signal amplitude exceeds a fixed threshold:

if |amplitude| > threshold → Detection!

How it works:

  1. Set a fixed amplitude threshold value
  2. Monitor continuous seismic data
  3. Trigger detection when amplitude exceeds threshold
  4. Mark detection end when amplitude drops below threshold

Why Simple Thresholding Fails

This basic approach has fundamental limitations:

  • Cannot distinguish earthquake types - any signal above threshold triggers detection
  • No waveform analysis - treats all signals equally
  • Fixed sensitivity - same threshold for all conditions
  • Distance dependent - same earthquake has different amplitudes at different stations
  • Noise vulnerable - any spike triggers detection

Critical Issue: No threshold value works well - set it low and get many false alarms, set it high and miss real earthquakes!

Detection Performance Issues

Common problems with amplitude threshold detection:

Problem Example
False Positives Vehicles, explosions, machinery
Missed Events Small/distant earthquakes
No Classification Can't identify source type
Manual Tuning Threshold needs constant adjustment

Bottom Line: Simple amplitude thresholding is outdated and ineffective for modern seismic monitoring. It's why advanced methods like matched filtering were developed.