Workflow and Strategy

Without AIMBAT

MCCC¹ requires narrow time windows centred on the initial phase arrival to produce accurate results. Without a tool like AIMBAT, phase arrivals must be picked on each seismogram individually — a time-consuming task illustrated by the stacked steps in the flowchart below:

flowchart TD
  A@{ shape: circle, label: "Start"} --> B>Import seismograms];
  B --> C[Select suitable filter parameters]
  C --> D[Choose high quality seismograms to use for MCCC]
  D --> E@{ shape: processes, label: "Individually pick phase arrival for seismograms 1...N"}
  E --> F[Choose time window for MCCC]
  F --> G>Run MCCC to align seismograms]

With AIMBAT

AIMBAT² stacks all seismograms aligned on an initial pick, then cross-correlates each seismogram against that stack to refine arrivals simultaneously across the array. Parameters and picks are improved iteratively before a final MCCC run.

flowchart TD
  A@{ shape: circle, label: "Start"}
  A --> B>Import seismograms containing initial picks t0];
  B --> F
  E[Adjust AIMBAT parameters];
  E --> F>Run ICCS with initial/updated parameters]
  F --> G[Inspect results of alignment];
  G --> H{"Continue
          with
          MCCC?"}
  H ---->|Yes| M>"Run MCCC for final alignment"];
  H -->|No| E;

Strategy

1. Change one parameter at a time and run ICCS to observe the effect before making further adjustments.
2. Take snapshots often, with a comment describing the current state. They are lightweight and easy to roll back to.
3. Do not focus too much on individual poorly-aligned seismograms — use autoflip and autoselect to let the algorithm handle them.

ICCS running modes

ICCS has two optional flags:

• Autoflip: automatically toggles the flip parameter for seismograms whose maximum absolute correlation with the stack is negative (i.e. inverted polarity).
• Autoselect: automatically sets select=False for seismograms poorly correlated with the stack, and restores them to select=True if they improve in a subsequent iteration.

The flip parameter controls polarity when preparing seismograms for the stack. The select parameter controls whether a seismogram is included in the stack — but all seismograms are cross-correlated against the stack regardless of their select status. A deselected seismogram can therefore recover automatically if parameter changes bring it into alignment.