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We produced a globally distributed catalog of earthquakes and nuclear explosions with calibrated hypocenters, referred to as the Global Catalog of Calibrated Earthquake Locations (GCCEL). This dataset currently contains 18,782 events in 289 clusters with >3.2 million arrival times observed at 19,258 stations. The term “calibrated” refers to the property that the hypocenters are minimally biased by unknown Earth structure. In addition, we calculate uncertainties using empirically determined variability of the arrival-time data itself, specific to each calibrated cluster of hypocenters. Outliers in the arrival-time dataset are removed based on measured variability of the data. In each cluster, we estimate the empirically determined uncertainty for each set of station-phase arrival times. We use a version of the hypocentroidal decomposition multiple event relocation algorithm specifically adapted for calibrated relocations of clusters of seismic events. Most clusters are calibrated by fitting the subset of direct crustal first arrivals (Pg and Sg) with a locally appropriate travel-time model to estimate the cluster hypocentroid. A few clusters are calibrated by aligning the pattern of relative locations in space and time with one or more events for which a ground-truth hypocenter is available from an independent source with known uncertainty, such as a nuclear explosion. Epicentral uncertainties in GCCEL typically range from 1 to 5 km with a 90% confidence interval. Most events have depth constraint from one or more sources, usually with an uncertainty of ≤5 km. GCCEL is a significant resource for research at local, regional, and global scales because it provides minimally biased absolute hypocenters, meaningful associated error estimates, and curated arrival times as a reference dataset that can be used as prior constraints in the development of new regional, national, and global earthquake catalogs; validation of new location techniques; and the generation of advanced Earth models.

Knowing the orientation of horizontal components of seismic sensors is important for many seismological applications such as waveform modeling, receiver function analysis, and shear-wave splitting. We determined the sensor orientations for broadband seismic stations belonging to the Iranian National Seismic Network (INSN) and the Iranian Seismological Center (IRSC) to enable such studies. For both networks, we have catalogs of event-based seismic waveforms of Iranian earthquakes. Sensor orientations were found by P-wave energy minimization on the transverse component and validated by long-period waveform modeling of events with well-constrained source parameters. We obtained stable sensor orientations for 28 (of 29) INSN sites and for 66 (of 92) IRSC sites. About 75% and 59% of all INSN and IRSC orientation estimates, respectively, are oriented within 15° of true north leaving many sites with largely misoriented sensors. We found temporally changing sensor orientations for 36 (of 121) sites.