Rewrite bb-sim on dask and switch to the site-calculation models

Two changes to the same function body, which is why they are one commit.

**Larger than memory.** `bb-sim` read both waveform files entirely into
memory and looped over the three components in Python. Now LF and HF are
opened lazily, the common stations are selected on the *backend* arrays
before chunking -- selecting after chunking makes station reordering an
all-to-all dask shuffle, which materialises the whole array -- and the
recombination runs per chunk under `map_blocks`. Chunking is over
stations only, so each chunk holds complete traces for resampling,
alignment and filtering.

`resample_signal` and `align_datasets` replace the old pad-and-align:
the two legs no longer have to share a timestep, so an SW4 LF run at one
dt can be combined with HF at another. `relabel_hf_components` maps HF's
090/000/ver onto LF's x/y/z once, up front.

**Site amplification.** Replaces `qcore.siteamp_models.cb_amp_multi`
with the `site-calculation` models, selected by `bb.site_amp_version`:
CB2014 as before, or BA2018. The amplification is now constrained to an
explicit [fmin, fmax] band with logarithmic tapers at both ends, which
is what the two new `fhightop` and `fmax` parameters are for -- the old
code had a lowpass taper only.

`site_amp_version` becomes an enum rather than a free string. It was
previously declared, defaulted to "2014", and read by nothing at all.

The shared broadband parameters move from each defaults version into
root; the versions now carry only `flo`, which is the one value that
genuinely differs between them.

Station-dimension coordinates -- `supergrid_depth` among them -- ride
through `map_blocks` untouched, which is why the supergrid penetration
is carried as a coordinate rather than a data variable.

This changes broadband results: different site amplification model, and
a highpass taper where there was none.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Author: lispandfound

pyproject.toml

@@ -16,6 +16,7 @@ dependencies = [
   "nshmdb>=2026.09.1",
   "oq_wrapper>=2025.12.3",
   "qcore-utils>=2025.12.2",
+  "site-calculation>=2026.7.1",
   "source_modelling>=2026.08.1",
   # Data Formats
   "geopandas",
@@ -141,6 +142,7 @@ known-first-party = [
   "IM",
   "mera",
   "velocity_modelling",
+  "site_calculation",
 ]
 
 [tool.ruff.lint.per-file-ignores]

tests/test_realisation.py

@@ -604,16 +604,23 @@ def test_emod3d(tmp_path: Path) -> None:
 def test_broadband_parameters(tmp_path: Path) -> None:
     test_realisation = tmp_path / "realisation.json"
     broadband_parameters = realisations.BroadbandParameters(
-        flo=0.5, fmidbot=0.5, fmin=0.25, site_amp_version="2014"
+        flo=0.5,
+        fmidbot=0.5,
+        fmin=0.2,
+        fhightop=100.0,
+        fmax=101.0,
+        site_amp_version=schemas.SiteAmpModel.BA2018,
     )
     broadband_parameters.write_to_realisation(test_realisation)
     with open(test_realisation, "r") as realisation_handle:
         assert json.load(realisation_handle) == {
             "bb": {
                 "flo": 0.5,
                 "fmidbot": 0.5,
-                "fmin": 0.25,
-                "site_amp_version": "2014",
+                "fmin": 0.2,
+                "fhightop": 100.0,
+                "fmax": 101.0,
+                "site_amp_version": "ba2018",
             }
         }
     assert (

uv.lock

@@ -1526,3 +1526,9 @@ hf_velocity_model_1d:
       rho: 3.33
       Qp: 394.80
       Qs: 197.40
+bb:
+  fmin: 0.2
+  fmidbot: 0.5
+  fhightop: 100.0
+  fmax: 101.0
+  site_amp_version: "ba2018"

workflow/default_parameters/root/defaults.yaml

@@ -3,6 +3,3 @@ resolution:
   resolution: 0.1
 bb:
   flo: 1.0
-  fmidbot: 0.5
-  fmin: 0.25
-  site_amp_version: "2014"

workflow/default_parameters/v24_2_2_1/defaults.yaml

@@ -3,6 +3,3 @@ resolution:
   resolution: 0.2
 bb:
   flo: 0.5
-  fmidbot: 0.5
-  fmin: 0.25
-  site_amp_version: "2014"

workflow/default_parameters/v24_2_2_2/defaults.yaml

@@ -3,6 +3,3 @@ resolution:
   resolution: 0.4
 bb:
   flo: 0.25
-  fmidbot: 0.5
-  fmin: 0.25
-  site_amp_version: "2014"

workflow/default_parameters/v24_2_2_4/defaults.yaml

@@ -1,9 +1,6 @@
 ---
 bb:
   flo: 1.0
-  fmidbot: 0.5
-  fmin: 0.2
-  site_amp_version: "ba2018"
 velocity_model:
   # Overrides the root default of 2.0 km, which is an EMOD3D value and has no
   # absorbing layer to clear. Two criteria bear on this number, and only the

workflow/default_parameters/v26_7_1Hz/defaults.yaml

@@ -1366,10 +1366,15 @@ class BroadbandParameters(RealisationConfiguration):
     flo: float
     """low/high frequency cutoff."""
     fmidbot: float
-    """fmidbot for site amplification"""
+    """fmidbot for the site amplification lowpass taper."""
     fmin: float
-    """fmin for site amplification."""
-    site_amp_version: str
+    """fmin for the site amplification lowpass taper."""
+    fhightop: float
+    """fhightop for the site amplification highpass taper."""
+    fmax: float
+    """fmax for the site amplification highpass taper."""
+    site_amp_version: schemas.SiteAmpModel
+    """The site amplification model to apply."""
 
 
 @dataclasses.dataclass

workflow/realisations.py

@@ -35,6 +35,13 @@ class Stype(StrEnum):
     seki = "seki"
 
 
+class SiteAmpModel(StrEnum):
+    """Site amplification models for broadband simulation."""
+
+    CB2014 = "cb2014"
+    BA2018 = "ba2018"
+
+
 class KModel(IntEnum):
     """Correlation length models for genslip."""
 
@@ -1168,7 +1175,13 @@ def _corners_to_array(corners_spec: list[dict[str, float]]) -> np.ndarray:
         Literal("fmin", description="fmin for site amplification"): And(
             NUMBER, _is_non_negative
         ),
-        "site_amp_version": str,
+        Literal("fhightop", description="fhightop for site amplification"): And(
+            NUMBER, _is_non_negative
+        ),
+        Literal("fmax", description="fmax for site amplification"): And(
+            NUMBER, _is_non_negative
+        ),
+        "site_amp_version": Use(SiteAmpModel),
     }
 )