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. The diagram below reflects the original AIMBAT workflow. In modern AIMBAT, snapshots provide save points throughout the process, making the workflow more flexible: MCCC can be run at any point, not only as a final step, and ICCS and MCCC runs may alternate as parameters are refined. Results can be exported from any snapshot; running MCCC before the final export is usual but not required.

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. There is no limit on how many snapshots an event can have — use them as freely as version-control commits.
3. Do not focus too much on individual poorly-aligned seismograms — use autoflip and autoselect to let the algorithm handle them.
4. Export picks whenever the dataset is in a useful state — not only at the end. ICCS picks are directly usable, and a snapshot taken at any stage is sufficient to produce output.

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.

MCCC running modes

MCCC has one optional flag:

• --all: includes deselected seismograms in the inversion. By default, only seismograms with select=True participate. Passing --all computes picks and quality metrics for every seismogram, regardless of selection state, which is useful when you want timing estimates for all stations even if some were excluded from the ICCS stack.

Use --all with care: deselected seismograms are typically excluded because they are noisy or misaligned, and including them may degrade the inversion for the rest of the array.