Exporters¶

qseek export writes the detections of a run into the input formats of other programs. Use it to relocate the detections with HypoDD or to invert for a 1D velocity model with VELEST.

Export a run¶

Start the export in the directory of the search configuration, so that relative paths in the configuration of the run, e.g. of the velocity model, are found:

qseek export list                                 # list the exporters
qseek export hypodd my-search/ my-search-hypodd/  # export the run my-search/

The export directory must not exist. --force replaces an existing directory, but only after the export succeeded. --config reads the settings of the exporter from a JSON file:

qseek export hypodd my-search/ my-search-hypodd/ --config hypodd.json

Each exporter writes its settings to export_info.json in the export directory, so you can reproduce the export.

HypoDD¶

HypoDD relocates earthquakes with the double-difference method (Waldhauser and Ellsworth, 2000). It inverts the travel time differences of event pairs at common stations, so errors of the velocity model largely cancel for close events and the relative locations of a cluster sharpen.

qseek export hypodd writes a complete project folder for HypoDD 2.1: the picks, the stations, the velocity model and the control files of ph2dt and hypoDD. Run it with the HypoDD binaries:

qseek export hypodd my-search/ my-search-hypodd/
cd my-search-hypodd/
HYPODD_BIN=~/src/HypoDD/bin ./run.sh

run.sh runs ph2dt and hypoDD, then converts the relocations with hypodd_results.py:

What the export does:

• Selection: picks with a confidence of at least 0.3 and a residual of at most 1 s to the modeled arrival, detections with at least 6 of these picks. The confidence is the pick weight in HypoDD. max_rms and min_distance_border select detections by their residual RMS and their distance to the border of the search volume.
• Velocity model: the 1D model of the ray tracer of the P phase, from Pyrocko Cake or fast marching. Gradient layers are split into constant velocity layers of at most 500 m, each with the harmonic mean velocity of its depth range. A constant velocity becomes HypoDD's straight-ray model.
• Data: catalog differential times, which ph2dt forms from the picks. With cross_correlation, the export also correlates the waveforms of close events for differential times in dt.cc. Station corrections of the run are not applied, the double-difference method does not need them.

On the Campi Flegrei example of the quick start, 20 May 2024, Qseek exports 424 detections with 5893 picks and hypoDD relocates 340 of them in about 2 s.

The guide relocate with HypoDD explains how to check and tune the relocation, how the export handles depths, elevations and air-quakes, every column of the CSV file and all settings.

VELEST¶

VELEST inverts the travel times of local earthquakes jointly for their hypocenters, a 1D velocity model and station corrections: the minimum 1D model (Kissling et al., 1994). It also locates single events in a given model.

qseek export velest writes a VELEST project folder for the joint inversion. The export asks for the selection of the detections and picks:

Qseek writes these files:

What the export does:

• Pick weights: VELEST weights picks by classes. The pick confidence becomes class 0 from 0.8, class 1 from 0.6, class 2 from 0.4 and class 3 below 0.4.
• Velocity model: the layers of the Pyrocko Cake model of the first ray tracer, with their P and S velocities. The export needs a Cake ray tracer as the first ray tracer of the search.
• Control file: joint inversion (isingle=0) with 9 iterations (ittmax), the velocity model updated every third iteration (invertratio=3) and a Vp/Vs ratio of 1.65. The reference point is the center of the search volume; VELEST counts longitudes positive to the west, so its sign is flipped. Station elevations and station corrections are off.

Run VELEST in the project folder. Build it from the src/VELEST folder of the REAL repository and copy the region files from its VELEST demo:

cd my-search-velest/
cp ~/src/REAL/demo_real/VELEST/region* .
velest

VELEST writes its report to main.out, the final hypocenters to final.cnv and the station corrections to stacor.dat. To only locate the events in the initial model, set isingle to 1 in velest.cmn. Check the parameters of velest.cmn against the VELEST documentation before you invert; the control file has many more options than the export sets.