Absolute Pressure Gauge Research Articles

High‐Frequency Tsunamis Excited Near Torishima Island, Japan, Observed by Distributed Acoustic Sensing

AbstractRecent distributed acoustic sensing (DAS) experiments in ocean areas throughout the world have accumulated records for various wavefields. However, there are few tsunami records because tsunami observation depends on the DAS experimental period and its location. From continuous DAS records, we found tsunami signals at a frequency band of 5–30 mHz, which correspond to high‐frequency components of tsunamis and their propagation velocities differ from low‐frequency tsunamis. We estimated time series of the tsunami excitations at the source using the DAS records, which are consistent with those using records of ocean‐bottom absolute pressure gauges. Our study suggests that DAS records can be used for detecting tsunami propagations in the regions where other geophysical instruments are not available, and contribute to elucidating their excitation mechanisms.

Capacitance-based absolute pressure gauge for beamline vacuum measurement applications

For low-pressure measurements, capacitance diaphragm-based absolute pressure gauges are used owing to their high accuracy, media independence, and simplistic design. Catering to the general requirements of synchrotron beamline vacuum measurements, a capacitance diaphragm-based absolute pressure gauge is designed, developed, tested, and calibrated. The sensor is having electrode assembly which forms a dual capacitor with the gauge body. The two capacitances are used in post-processing to reduce the noise levels and to enhance the precision and accuracy of the measurements. The reference side is at high vacuum of the level 5 × 10-5 Pa. The vacuum of the reference side is generated using a Turbo Molecular Pump and is sustained by pinching-off the reference side at this vacuum. A getter pump is provided and energized for improving the vacuum which otherwise gets deteriorated due to outgassing in the reference region of the gauge. The fabrication methods adopted for fabricating the gauge are novel. The diaphragm is fabricated from bulk material using the electrical discharge method (EDM). This helped in achieving a perfect diaphragm with linear deflection with pressure variation and attained a 100% success rate. Unlike the fabrication by welding of plate, this method is robust, economical, and helped in achieving similar properties across the gauges. The second innovation is in the fabrication of electrode assembly. Unlike commonly used electrodeposited electrodes; the presented technique used copper plates which sandwich the Alumina dielectric. The plates are bolted/brazed/welded across the ceramic disc with the help of pins which also help in the parallel connection of the dual capacitors are described later. This made this method of fabrication largely rejection free with the potential of repairs and testing with different plate configurations. This paper is presenting the design, production, and calibration of the gauge using these fabrication techniques for 1 × 103 Pa to 1 × 105 Pa.

Earthquake Rupture and Tsunami Generation of the 2015 Mw 5.9 Bonin Event Revealed by In Situ Pressure Gauge Array Observations and Integrated Seismic and Tsunami Wave Simulation

AbstractOn September 1, 2015, an Mw 5.9 interplate earthquake occurred near the Bonin Trench. An array of in situ ocean‐bottom absolute pressure gauges (APGs) observed its tsunami generation field consisting of static and dynamic pressure changes due to tsunami and crustal deformation and due to seismic motion, respectively, under much higher station density than ever reported. We propose an approach to synthesize the pressure change inside the focal area, which reproduces the APG waveforms well. We further successfully estimate the finite fault model of the earthquake and constrain the rupture duration only from the APG data. The relatively low stress drop and seismic wave radiation from the fault model may suggest the nature of a tsunami earthquake. The in situ APGs have a large potential to reveal the broadband source process of the earthquake, which is essential to understand the seismotectonics in the subduction zone.

Fiscal measurement and the effects of atmospheric pressure variation: Small deviations and large risks

The production and transport of liquid and gaseous hydrocarbons have always been the object of studies to improve technologies and procedures, as they involve large volumes and high-value goods. There are several procedures, rules and regulations applied to the measurement of fluid flow, but its applicability may involve significant operating costs. The balance between requirements and costs led to the use of gauge pressure transmitters instead of absolute pressure gauges and assuming a constant atmospheric pressure value for parameterization of compensation algorithms. This solution simplifies the calibration process but can potentially impact measurement uncertainties because atmospheric pressure is not constant. This work quantifies these impacts and concludes that, for gas systems operating below 2000 kPa, the use of absolute pressure transmitters or the incorporation of in-line atmospheric pressure gauges is recommended. Above this value, the effects of atmospheric pressure variation do not have as much impact, but even in these cases the final uncertainty estimate of the measured gas volume must consider this source of additional uncertainties.

Tilt Observations at the Seafloor by Mobile Ocean Bottom Seismometers

We have developed a broadband ocean bottom seismometer (BBOBS) and its new generation (BBOBS-NX) with the penetrator sensor system since 1999. With them, we performed many practical observations to create a new research category of ocean bottom broadband seismology. As the next step in seafloor geophysical observation, the BBOBS and the BBOBS-NX can be a breakthrough in realizing a geodetic observation network on the seafloor. Although vertical displacement observation by the absolute pressure gauge has been widely conducted in recent years, other geodetic observations are rarely performed. A few trials to measure the seafloor tilt were performed, but those looked inadequate for practical observations. Note that the broadband sensor in our BBOBSs has a mass position signal output, which can be used to measure the tilt change. As the horizontal component noise level of the BBOBS-NX is good at a long period range, we expected it to be adequate for the tilt measurement. At the first evaluation, we performed a comparison with a water-tube tiltmeter. The result was comparable with a resolution of better than 1 µ radian. A practical observation at the south of Boso Peninsula (KAP3 site) was conducted as thein-situstudy from April, 2013. In January, 2014, a slow slip event (SSE) occurred near this site. The tilt data were processed by removing steps, mechanical relaxation, and tides. The results show a clear peak started from late December 2013. Two more 2 year-long tilt observations began in 2015: one was at the KAP3 site and another was off the Miyagi Prefecture at the slope to the Japan Trench. The latter was recovered in 2017 with about 1.5 years of data, which indicate a large continuous tilt up to several tens of µ radian. This amount of tilt can be explained by a similar already estimated SSE. Mobile tilt measurement at the seafloor can be a powerful tool to study SSEs, as they can be located above the source area and also possible to build an observation array for a practical study because of its low cost and ease of deployment compared with a seafloor borehole site.

The Alaska Amphibious Community Seismic Experiment

AbstractThe Alaska Amphibious Community Seismic Experiment (AACSE) is a shoreline-crossing passive- and active-source seismic experiment that took place from May 2018 through August 2019 along an ∼700 km long section of the Aleutian subduction zone spanning Kodiak Island and the Alaska Peninsula. The experiment featured 105 broadband seismometers; 30 were deployed onshore, and 75 were deployed offshore in Ocean Bottom Seismometer (OBS) packages. Additional strong-motion instruments were also deployed at six onshore seismic sites. Offshore OBS stretched from the outer rise across the trench to the shelf. OBSs in shallow water (<262 m depth) were deployed with a trawl-resistant shield, and deeper OBSs were unshielded. Additionally, a number of OBS-mounted strong-motion instruments, differential and absolute pressure gauges, hydrophones, and temperature and salinity sensors were deployed. OBSs were deployed on two cruises of the R/V Sikuliaq in May and July 2018 and retrieved on two cruises aboard the R/V Sikuliaq and R/V Langseth in August–September 2019. A complementary 398-instrument nodal seismometer array was deployed on Kodiak Island for four weeks in May–June 2019, and an active-source seismic survey on the R/V Langseth was arranged in June 2019 to shoot into the AACSE broadband network and the nodes. Additional underway data from cruises include seafloor bathymetry and sub-bottom profiles, with extra data collected near the rupture zone of the 2018 Mw 7.9 offshore-Kodiak earthquake. The AACSE network was deployed simultaneously with the EarthScope Transportable Array (TA) in Alaska, effectively densifying and extending the TA offshore in the region of the Alaska Peninsula. AACSE is a community experiment, and all data were made available publicly as soon as feasible in appropriate repositories.

Coupling Pressure Sensing with Optical Coherence Tomography to Evaluate the Internal Nasal Valve.

To evaluate endoscopic long-range optical coherence tomography system combined with a pressure sensor to concurrently measure internal nasal valve cross-sectional area and intraluminal pressure. A pressure sensor was constructed using an Arduino platform and calibrated using a limiter-controlled vacuum system and industrial absolute pressure gauge. Long-range optical coherence tomography imaging and pressure transduction were performed concurrently in the naris of eight healthy adult subjects during normal respiration and forced inspiration. The internal nasal valve was manually segmented using Mimics software and cross-sectional area was measured. Internal nasal valve cross-sectional area measurements were correlated with pressure recordings. Mean cross-sectional area during forced inspiration was 6.49 mm2. The mean change in pressure between normal respiration and forceful inspiration was 12.27 mmHg. The direct correlation between pressure and cross-sectional area as measured by our proposed system was reproducible among subjects. Our results demonstrate a direct correlation between internal nasal valve cross-sectional area and nasal airflow during inspiration cycles. Endoscopic long-range optical coherence tomography coupled with a pressure sensor serves as a useful tool to quantify the dynamic behavior of the internal nasal valve.

APMP key comparison of absolute pressure from 10 kPa to 110 kPa (APMP.M.P-K9)

This report describes the results of a key comparison of pneumatic pressure standards which was carried out at fourteen National Metrology Institutes (NMIs: NMIA, NSCL, PTB, NIM, VMI, CMS/ITRI, MSL, NMIJ/AIST, NMC A*STAR, NIMT, SCL, NIS, RCM-LIPI and KRISS) during the period of February 2010 to July 2012 within the framework of the Asia-Pacific Metrology Programme (APMP) in order to determine their degrees of equivalence at pressures in the range 10 kPa to 110 kPa in absolute mode. Among them, twelve NMIs' results were compared in the report. The pilot laboratory was Korea Research Institute of Standards and Science (KRISS). The degrees of equivalence in this comparison were transferred to the corresponding CC key comparison, CCM.P-K2. National Measurement Institute, Australia (NMIA) and Physikalisch-Technische Bundesanstalt (PTB) that participated in the CC comparison agreed to be link laboratories.Most of the participating institutes used pneumatic pressure balances as their pressure standards while two link laboratories used laser interferometer mercury manometers. Precise absolute pressure gauges were used as transfer standards (TSs). The precision pressure gauge has two Quartz-Resonant Pressure Transducers (Q-RPTs) inside. Two identical transfer packages (TS-A and TS-B) were circulated independently to reduce the time required for the measurements. During the comparison, intermediate measurements of two circulated transfer standards were carried out in the pilot laboratory after one or two NMIs measurement and third transfer standard (TS-C) was monitored for the stability characterization, also. The pressures of the comparison were (10, 30, 50, 70, 90, 100, 110) kPa. From the calibration results, the behaviours of the transfer standards during the comparison period were well characterized and it was concluded that the performance of the transfer standards were sufficient in the comparison pressure range except 10 kPa. The TSs used in this comparison were not suitable for the low pressure measurement like 10 kPa because of low display resolution of TS (1 part in 105 at 10 kPa). The degrees of equivalence of each national measurement standard were expressed quantitatively by two terms, deviations from the key comparison reference values (KCRVs) and pair-wise differences of their deviations together with the associated uncertainties. The pneumatic pressure standards in the range 30 kPa to 110 kPa for absolute mode of all participating NMIs were found to be equivalent within their claimed uncertainties.Main textTo reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Post-seismic response of the outer accretionary prism after the 2010 Maule earthquake, Chile

AbstractTo investigate the dynamic response of the outer accretionary prism updip from the patch of greatest slip during the 2010 Mw 8.8 Maule earthquake (Chile), 10 ocean-bottom seismometers (OBSs) were deployed from May 2012 to March 2013 in a small network with an inter-instrument spacing of 7–10 km. Nine were recovered, with four recording data from intermediate-band three-component seismometers and differential pressure gauges, and five recording data from absolute pressure gauges (APGs). All instruments were also equipped with fluid flow meters designed to detect very low rates of flow into or out of the seafloor. We present hypocenters for local earthquakes that have S-P times <17 s (i.e., within ∼125 km of the network), with a focus on events located beneath or near the network. Most of the seismicity occurred either near the boundary between the active accretionary prism and continental basement or in the outer rise seaward of the trench. For many outer-rise earthquakes, the P and S arrivals are followed by a distinctive T-phase arrival. Very few earthquakes, and none located with hypocenters deemed “reliable,” were located within the active accretionary prism or on the underlying plate boundary. Nonvolcanic tremor-like pulses and seafloor pressure transients (but no very-low-frequency earthquakes or fluid flow) were also detected. Many of the tremor observations are likely T-phases or reverberations due to soft seafloor sediments, although at least one episode may have originated within the accretionary prism south of the network. The transient seafloor pressure changes were observed simultaneously on three APGs located over the transition from the active prism to the continental basement and show polarity changes over short distances, suggesting a shallow source. Their duration of several hours to days is shorter than most geodetic transients observed using onshore GPS networks. The results demonstrate the need for densely spaced and large-aperture OBS networks equipped with APGs for understanding subduction zone behavior.

Time‐Dependent Behavior of a Near‐Trench Slow‐Slip Event at the Hikurangi Subduction Zone

AbstractStudying offshore slow‐slip events (SSEs) along subduction zone interfaces is important for constraining the overall slip budget and potential for seismic slip and the relationship with large megathrust earthquakes. Models using only onshore data increasingly lack model resolution the further from the shore the SSE occurs. In this study, we combine data from the Hikurangi Ocean Bottom Investigation of Tremor and Slow Slip seafloor absolute pressure gauge (APG) network with daily position time series from New Zealand's GeoNet to create time‐dependent models of slip during the 2014 Gisborne, New Zealand SSE using the Network Inversion Filter. We compare models assuming heterogeneous versus homogenous elastic properties to explore their influence on our models. The time‐dependent results show that slip uncertainties under the APGs drop by about 23%. We also find that the peak value of slip increases with heterogeneous elastic properties as compared to homogenous models. The inclusion of the offshore APG data in our models places more slip near the trench and detects a more defined migration of slip, especially in the heterogeneous model. These differences are important for interpreting the relationship between the SSE and associated tremor, which occurs after the peak SSE slip rate. Additionally, we use a static “potency bounding” technique in order to gauge the range of models that can fit the data. This analysis demonstrates that the inclusion of offshore data helps to substantially narrow the range of plausible slip models.

ADSORPTION OF BENZENE, ACETONE AND CARBON TETRACHLORIDE VAPORS ON MICROPOROUS CARBON ADSORBENT FAS-3

In this paper, the study of the adsorption of organic matter vapors (benzene, carbon tetrachloride, acetone) on the microporous carbon adsorbent FAS-3 in the region of pressures from 0.1 PA to 0.1 MPa and temperatures from 293 to 313 K was conducted, which showed sufficiently high adsorption characteristics of the used adsorbent in comparison with traditional absorbers. Microporous carbon adsorbent FAS-3 is quite new and still not fully understood. The purpose of this study was to determine the parameters of the adsorbent FAS-3, as well as the study of the processes of vapor adsorption of various organic substances on it. The microporous carbon adsorbent FAS-3, obtained on the basis of furfural, was used in the work. Obtaining spherical granules of the adsorbent FAS-3 was carried out in the result of liquid molding of a copolymer of furfural and epoxy resin on the basis of a fundamentally new process of combining the stages of blending monomer, molding the mixture in spherical product of the cured pellets. The activation of spherical grains of FAS-3 was carried out in a rotary kiln by a mixture of water vapor and carbon dioxide at a temperature of 850-900°C to burning that was consistent with the development of porosity in the adsorbent. The equilibrium values of vapor adsorption of substances on FAS-3 were measured on the gravimetric vacuum unit developed in the Institute of Physical Chemistry and Electrochemistry of the Russian Academy of Sciences. Regeneration of the adsorbent was carried out for 6 h at a temperature of 623 K to a pressure of 0.1 Pa. The maximum absolute measurement error was ± 0.01 mmol / g with 95% confidence. Measurement of vapor pressure of organic substances within 0.13 Pa-0.13 MPa was carried out by absolute pressure gauges M10, M1000, developed and manufactured in the Institute of Physical Chemistry and Electrochemistry of the Russian Academy of Sciences. The pressure measurement error by the manometer M10 in the range of 0.13 to 1330 Pa was ±0.066 Pa, and the manometer M1000 in the range from 13 Pa to 130 kPa was ±4.0 Pa.

Seismicity at the Northern Hikurangi Margin, New Zealand, and Investigation of the Potential Spatial and Temporal Relationships With a Shallow Slow Slip Event

AbstractIn 2014–2015, the Hikurangi Ocean Bottom Investigation of Tremor and Slow Slip experiment deployed seafloor absolute pressure gauges and ocean bottom seismometers directly above a large slow slip event, allowing examination of the relationship between slow slip and earthquakes in detail. Hikurangi Ocean Bottom Investigation of Tremor and Slow Slip data were combined with nearby existing land stations to create a catalog of microseismicity consisting of 2,300 earthquakes ranging in magnitude between 0.5 and 4.7 that is complete to magnitude 1.5, yielding almost twice as many events as detected by the onshore networks alone. This greatly improves the seismicity catalog for this active subduction zone margin, especially in the offshore portion that was difficult to study using only the inland permanent seismic network. The new locations for the events within the footprint of the offshore network show that earthquakes near the trench are systematically shallower than and NW (landward) of their locations using only land‐based stations. Our results indicate that Hikurangi seismicity is concentrated in two NE‐SW bands, one offshore beneath the outer forearc wedge, one onshore beneath the eastern Raukumara Peninsula, and the majority of earthquakes are within the subducting Pacific plate with a smaller percent at the plate interface. We find a 20‐km wide northeast trending gap in microseismicity between the two bands and beneath the inner forearc wedge and this gap in seismicity borders the downdip edge of a slow slip patch.

Seismic Observation of Tsunami at Island Broadband Stations

AbstractPrevious studies have reported seismic observations of tsunami recorded at island broadband stations. Coastal loading by the tsunami can explain them. For further quantification, we model tsunami propagation assuming an axisymmetric structure: a conical island with a flat ocean floor. The total tsunami wavefield can be represented by superposition between an incident tsunami wave and the scattering. The ground deformation due to the total tsunami wavefield at the center is calculated using static Green's functions for elastic half‐space with a first‐order correction for bathymetry. By fitting the modeled displacement to observed seismic data, we can infer the incident tsunami wave, which can be interpreted as the virtual tsunami amplitude without the conical island. First, we apply this new method to three components of seismic data at a volcano island, Aogashima, for the 2015 Torishima‐Oki tsunami earthquake. The estimated tsunami amplitude from the vertical component is consistent with the offshore array observation of absolute pressure gauges close to the island (1.5–20 mHz). The estimated incident azimuth from the three components is also consistent with ray theory. Second, we apply this method to seismic data at four island broadband stations in the Indian ocean for the 2010 Mentawai tsunami earthquake in Indonesia. Despite the limited observed frequency range from 0.5–2.0 mHz, the amplitudes and incident azimuths are consistent with past studies. These observations can complement offshore tsunami observations. Moreover, this method is applicable not only for a tsunami but also for background ocean infragravity wave activity.

Improving Forecast Accuracy With Tsunami Data Assimilation: The 2009 Dusky Sound, New Zealand, Tsunami

AbstractWe use tsunami waveforms recorded on deep water absolute pressure gauges (Deep‐ocean Assessment and Reporting of Tsunamis), coastal tide gauges, and a temporary array of seafloor differential pressure gauges (DPG) to study the tsunami generated by the 15 July 2009 magnitude 7.8 Dusky Sound, New Zealand, earthquake. We first use tsunami waveform inversion applied to Deep‐ocean Assessment and Reporting of Tsunamis seafloor pressure gauge and coastal tide gauge data to estimate the fault slip distribution of the Dusky Sound earthquake. This fault slip estimate is then used to generate synthetic tsunami waveforms at each of the DPG sites. DPG instruments are unfortunately not well calibrated, but comparison of the synthetic tsunami waveforms to those observed at each DPG site allows us to determine an appropriate amplitude scaling to apply. We next use progressive data assimilation of the amplitude‐scaled DPG observations to retrospectively forecast the Dusky Sound tsunami wavefields and find a good match between forecast and observed tsunami wavefields at the Charleston tide gauge station on the west coast of New Zealand's South Island. While an advantage of the data assimilation method is that no initial condition is needed, we find that our forecast is improved by merging tsunami forward modeling from a rapid W‐phase earthquake source solution with the data assimilation method.

The Impact of Realistic Elastic Properties on Inversions of Shallow Subduction Interface Slow Slip Events Using Seafloor Geodetic Data

AbstractWe examine the effects of topography and material heterogeneity on geodetic inversions of shallow slow slip at the Hikurangi Subduction Margin, New Zealand. Offshore vertical data from absolute pressure gauges constrain our results. Using a finite element code to generate our Green's functions, we find that topography has a relatively small effect, reducing the seismic potency by only about 5% when compared to a flat model. When material heterogeneity from a New Zealand‐wide seismic velocity model is taken into account, we find an extremely large effect, with the seismic potency increasing by 58% or more. In previous work, we found the opposite effect for deeper slip events, where models including elastic property variations result in ~20% more slip than when they are neglected. Our previous results for deeper events are consistent with a simplified model that considers the elastic property contrasts between a strong subducting slab and a weaker overriding plate. To understand the opposite behavior of our shallower models, we use synthetic forward models and view material property gradients in terms of additional body forces. We find that gradients in elastic properties can produce very different surface displacements near the source than simple contrasts, thus explaining the contrasting results for shallow slip events. Combined with our previous results for deeper events, this implies that neglecting material heterogeneity in slow slip inversions may result in overestimates in the amount of slip for deeper events and underestimates for shallow events.

Excitation Location and Seasonal Variation of Transoceanic Infragravity Waves Observed at an Absolute Pressure Gauge Array

AbstractAn array of 10 absolute pressure gauges (APGs) deployed in deep water 50 km east of Aogashima, an island in southern Japan, observed several isolated signals in the infragravity wave (IGW) frequency band (0.002–0.03 Hz) during boreal summer, whereas relatively high IGW energy persisted during boreal winter. The isolated IGW shows dispersion with a delay time of 4–5 days as a function of frequency. Here we estimate the excitation locations of IGWs for the two seasons with estimated incoming direction of IGW, calculation of transoceanic IGW trajectories and propagation times, and spatiotemporal variations of significant wave heights from WAVEWATCH III. In boreal summer, the isolated IGWs are primarily caused by IGW energies excited at the shoreline of South America, based on the following three observations: IGWs observed at the array originated from the east: the easterly ray path from the array reaches South America: and an event‐like IGWs were observed at the array when a storm approaches eastward to the shoreline of South America, in which the observed delay time of 4–5 days was also supported by the frequency‐dependent calculation of IGW propagation times. In boreal winter, the incessant IGWs consist of transoceanic IGW energies leaked from the shoreline, primarily from North America, and secondly from South America and the western Aleutian Islands.

Gas Permeation Properties of Asymmetric Polyimide Membranes Made by Ion–beam Irradiation

In this study, the gas permeance and selectivity of the asymmetric polyimide membrane with skin layer carbonized by He ions irradiation were measured using a high vacuum apparatus with a Baratron absolute pressure gauge at 76 cmHg and 35°C. Particutarly, we focused on the effects of the depth profile of the energy loss for the irradiating He ions in the skin layer on the gas permeation properties of the asymmetric membranes. Irradiation depth is gauged through the energy loss profile of the irradiating ions. The nature of the carbonised layer was investigated using AFM and ATR–FTIR. We demonstrated that the PO2 of the He+–irradiated membranes increased with the skin layer thickness and that the depth of the irradiating ions in the skin layer had a significant influence on the gas permeability and selectivity of the asymmetric membrane.

Slow slip near the trench at the Hikurangi subduction zone, New Zealand.

The range of fault slip behaviors near the trench at subduction plate boundaries is critical to know, as this is where the world's largest, most damaging tsunamis are generated. Our knowledge of these behaviors has remained largely incomplete, partially due to the challenging nature of crustal deformation measurements at offshore plate boundaries. Here we present detailed seafloor deformation observations made during an offshore slow-slip event (SSE) in September and October 2014, using a network of absolute pressure gauges deployed at the Hikurangi subduction margin offshore New Zealand. These data show the distribution of vertical seafloor deformation during the SSE and reveal direct evidence for SSEs occurring close to the trench (within 2 kilometers of the seafloor), where very low temperatures and pressures exist.

Array Observations of the 2012 Haida Gwaii Tsunami Using Cascadia Initiative Absolute and Differential Seafloor Pressure Gauges

The purpose of this article is to test the ability of the seafloor pressure sensors utilized in the Cascadia Initiative (CI) experiment (Toomey et al. , 2014) to provide useful recordings of tsunamis, and to compare the performance of the different types of seafloor pressure sensors for long‐period recordings. These tests are performed through analysis of CI seafloor pressure recordings of the 2012 Haida Gwaii tsunami. Seafloor pressure measurements are a central part of tsunami warning systems. Deep‐ocean Assessment and Reporting of Tsunamis (DART) buoy systems, designed by National Oceanic and Atmospheric Administration (NOAA), are equipped with seafloor pressure sensors (also referred to as bottom pressure recorders [BPRs]), providing tsunami data in real time (Eble and Gonzalez, 1991; Gonzalez et al. , 1998; Bernard et al. , 2001; Meinig et al. , 2005; Titov et al. , 2005; Mofjeld, 2009; Rabinovich and Eble, 2015). The DART instruments are widely spaced in deep water (typically >2700 m) along coastal regions and near subduction zones. Cabled BPR arrays are becoming more common, such as the BPR array of NorthEast Pacific Time‐Series Undersea Networked Experiments (NEPTUNE)‐Canada ocean observatory (Thomson et al. , 2011), the Japan Agency for Marine‐Earth Science and Technology (JAMSTEC) BPR array (Baba et al. , 2004; Saito et al. , 2010), and the BPR array in the Cascadia basin (Rabinovich et al. , 2011). Observations of tsunamis have also been made serendipitously on pressure gauges accompanying a variety of nontsunami field programs (e.g., Drushka et al. , 2008; Lin et al. , 2015). In this study, we use seafloor pressure measurements from absolute pressure gauges (APGs), differential pressure gauges (DPGs), and DART BPRs to study the tsunami caused by the 2012 Haida Gwaii earthquake. The APG, used by the DART and increasingly in other oceanographic studies (Ito et al. , 2011; Chadwick et al. …

The sources of deep ocean infragravity waves observed in the North Atlantic Ocean

Infragravity waves are long-period (25–250 s) ocean surface gravity waves generated in coastal zones through wave-wave interactions or oscillation of the breaking point. Most of the infragravity wave energy is trapped or dissipated near coastlines, but a small percentage escapes into the open oceans. The source of deep ocean infragravity waves is debated, specifically whether they come mostly from regions with strong source waves or from sites with particular morphologies/orientations. We correlate measurements of infragravity waves in the deep North Atlantic Ocean with infragravity wave generation parameters throughout the Atlantic Ocean to find the dominant sources of deep ocean infragravity wave energy in the North Atlantic Ocean. The deep ocean infragravity wave data are from a 5 year deployment of absolute pressure gauges west of the Azores islands (37°N, 35°W) and shorter data sets from seafloor tsunami gauges (DART buoys). Two main sources are identified: one off of the west coast of southern Europe and northern Africa (25°N–40°N) in northern hemisphere winter and the other off the west coast of equatorial Africa (the Gulf of Guinea) in southern hemisphere winter. These regions have relatively weak source waves and weak infragravity wave propagation paths to the main measurement site, indicating that that the site morphology/orientation dominates the creation of deep ocean infragravity waves. Both regions have also been identified as potential sources of global seismological noise, suggesting that the same mechanisms may be behind the generation of deep ocean infragravity waves and global seismological noise in the frequency band from 0.001 to 0.04 Hz.