5:15 PM - 6:45 PM
[STT37-P02] Development of long-term broadband OBS using a glass sphere pressure housing
Keywords:Pop-up-type ocean bottom seismometer with a glass sphere housing, Development of a new power-saving recorder, Installing broadband sensor into OBS
The development of cabled seafloor seismic observation networks in recent decades has enabled seismologists to access offshore seismic data and facilitated the development of ocean-bottom seismology. However, cabled networks have disadvantages in the flexibility of station geometry and spatial density, as well as sensor replaceability. Therefore, pop-up-type OBS (ocean bottom seismometers) observation remains significant for advanced hypocenter determination and broadband observation above earthquake activities.
The pop-up-type OBS system traditionally uses a glass sphere pressure housing. After 2000, by replacing a pressure housing from glass with titanium, long-term OBS (LTOBS) which can record over a year, was developed, and now LTOBS is operated by equipping a broadband sensor. On the other hand, in some cases, there may be an insufficient number of broadband LTOBSs for deploying a network. Then, we explored developing a new glass-type OBS which enables us to the long-term and broadband observation.
For long-term broadband observation, it is necessary to reduce batteries for the recorder and then secure the space of batteries for the broadband sensor because the volume of the glass sphere housing is fundamentally small. From the above background, we have developed a new power-saving recording system and repeated tests at the ocean bottom. The new recorder features power-saving by mounting a low-power A/D converter, automatic clock correction using an internal GPS module, and a wireless connection with the user’s device. We succeeded in further power saving by cutting modules’ power during the recording term. These thorough power savings enable us to long-term observation over one year and then secure the space of batteries for the broadband sensor.
In this presentation, we report a first observation of the glass-type broadband OBS equipping the Trillium Compact Horizon 120 (120 seconds, Nanometrics). We deployed OBS at Sanriku-oki in May 2023 and recovered in November. Analog signals were continuously converted by a 24-bit A/D converter with a 100-Hz sampling rate and recorded to the storage. Although the quality of the data has not yet been assessed in this abstract, we have confirmed seismograms are recorded well by each component. We will investigate data quality by comparing data parallelly recorded by neighbor LTOBSs, which equip the Trillium Compact 20 (20 seconds, Nanometrics) or 1LE-3Dlite sensors (1 Hz, Lenartz).
The pop-up-type OBS system traditionally uses a glass sphere pressure housing. After 2000, by replacing a pressure housing from glass with titanium, long-term OBS (LTOBS) which can record over a year, was developed, and now LTOBS is operated by equipping a broadband sensor. On the other hand, in some cases, there may be an insufficient number of broadband LTOBSs for deploying a network. Then, we explored developing a new glass-type OBS which enables us to the long-term and broadband observation.
For long-term broadband observation, it is necessary to reduce batteries for the recorder and then secure the space of batteries for the broadband sensor because the volume of the glass sphere housing is fundamentally small. From the above background, we have developed a new power-saving recording system and repeated tests at the ocean bottom. The new recorder features power-saving by mounting a low-power A/D converter, automatic clock correction using an internal GPS module, and a wireless connection with the user’s device. We succeeded in further power saving by cutting modules’ power during the recording term. These thorough power savings enable us to long-term observation over one year and then secure the space of batteries for the broadband sensor.
In this presentation, we report a first observation of the glass-type broadband OBS equipping the Trillium Compact Horizon 120 (120 seconds, Nanometrics). We deployed OBS at Sanriku-oki in May 2023 and recovered in November. Analog signals were continuously converted by a 24-bit A/D converter with a 100-Hz sampling rate and recorded to the storage. Although the quality of the data has not yet been assessed in this abstract, we have confirmed seismograms are recorded well by each component. We will investigate data quality by comparing data parallelly recorded by neighbor LTOBSs, which equip the Trillium Compact 20 (20 seconds, Nanometrics) or 1LE-3Dlite sensors (1 Hz, Lenartz).