Noise Characteristics of High-Rate Multi-GNSS for Subdaily Crustal Deformation Monitoring

High-rate GPS (Global Positioning System) has the potential to record crustal motions on a wide subdaily timescale from seconds to hours but usually fails to capture subtle deformations which are often overwhelmed by the centimeter noise of epoch-wise GPS displacements. We hence investigated high-rate multi-GNSS (Global Navigation Satellite System) by processing 1Hz GPS/GLONASS/BeiDou data at 15 static stations over 24days and also those from the 8 August 2017 Jiuzhaigou M(w)6.5 earthquake. In contrast to high-rate GPS, its further integration with GLONASS/BeiDou reduces near uniformly the power spectral densities (PSDs) of 1Hz displacement noise by 4-6dB over the periods from a few seconds to half of a day, and orbital repeat time (ORT) filtering on all GNSS further again leads to a 2 more decibel decline of the PSDs over the periods of a few tens of seconds to minutes. BeiDou ORT filtering, however, takes effect mainly on the periods of over 2,000s due to the high altitudes of Inclined Geosynchronous Satellite Orbiters/Geosynchronous Earth Orbiters. Multi-GNSS integration is on average as effective as GPS ORT filtering in reducing PSDs for the periods of a few tens of seconds to minutes while desirably can further decrease the PSDs on almost all other periods by 3-4dB thanks to the enhanced satellite geometry. We conclude that the introduction of more GNSS into high-rate solutions and its augmentation by ORT filtering benefit the discrimination of slight deformations over a broad subdaily frequency band.