Updated Magnitude Scales for Mars

2020 ◽  
Author(s):  
Maren Böse ◽  
Simon Stähler ◽  
Domenico Giardini ◽  
Savas Ceylan ◽  
John Clinton ◽  
...  
Keyword(s):  
High Frequency ◽  
Body Wave ◽  
Secondary Phase ◽  
Scaling Relations ◽  
Seismic Events ◽  
Martian Surface ◽  
Broadband Seismometer ◽  
Noise Characteristics ◽  
Magnitude Scales ◽  
One Year

<p>About one year after the successful deployment of the InSight (Interior exploration using Seismic Investigations, Geodesy and Heat Transport) very-broadband seismometer on the Martian surface and the identification of several hundreds of seismic events in the current InSight catalogue, we revise the pre-launch magnitude relations in Böse et al. (2018) to account for the seismic and noise characteristics observed on Mars. The data collected so far indicate that (1) marsquakes are characterized by energy between ~0.1-10Hz; (2) neither surface-wave nor secondary phase arrivals have yet been identified; and (3) a class of high-frequency events exists that are visible mainly as an increased excitation of the 2.4Hz mode. In view of these observations, we up-date scaling relations for the spectral and body-wave magnitudes, and introduce a new magnitude scale for high-frequency events. We use these relations to determine that the magnitudes of events in the current InSight catalogue range between 1.0 and 4.0.</p>

Magnitude Scales for Marsquakes Calibrated from InSight Data

2021 ◽  
Author(s):  
Maren Böse ◽  
Simon C. Stähler ◽  
Nicholas Deichmann ◽  
Domenico Giardini ◽  
John Clinton ◽  
...  
Keyword(s):  
Body Wave ◽  
Secondary Phase ◽  
Martian Surface ◽  
S Wave ◽  
Broadband Seismometer ◽  
Noise Characteristics ◽  
Magnitude Scales ◽  
Strong Excitation ◽  
Wave Trains ◽  
Using Data

ABSTRACT In preparation for the National Aeronautics and Space Administration Interior exploration using Seismic Investigations, Geodesy and Heat Transport (InSight) Discovery Program mission, Böse et al. (2018) calibrated magnitude scales for marsquakes that incorporated prelaunch knowledge of Mars’ interior structure and the expected ambient and instrumental noise. Now, using data collected during the first two years after the successful deployment of the InSight very-broadband seismometer on the Martian surface, we revise these relations to account for the seismic and noise characteristics observed on Mars. The data collected so far (until 12 October 2020) include 485 seismic event detections and suggest that (1) marsquakes are characterized by energy between ∼0.1 and 10 Hz; (2) whereas first arriving P- and S-wave phases are regularly identified and assigned, both surface waves and secondary phase arrivals are extremely challenging to identify; (3) the majority of identified events include a strong excitation of an unexpected 2.4 Hz ground resonance; and (4) so-called high-frequency (HF) events exist that are visible mainly as guided Pg/Sg wave trains. In view of these observations, we update our scaling relations for the spectral and body-wave magnitudes, Mw,specMa, mbMa, and mbSMa, and introduce a new magnitude scale, M2.4Ma, for HF events. We use these scales to determine that the magnitudes of events in the current InSight version 5 catalog range between 1.1 and 3.7, with event-specific uncertainties σM ranging from 0.2 to 0.4. Because of the currently unclear interpretation of HF events, magnitude estimates for these events primarily serve as a relative comparison.

A note on discrepancies between local magnitude (ML) and microearthquake magnitude scales

1973 ◽  
Vol 63 (1) ◽  
pp. 315-319
Author(s):  
Wayne Thatcher
Keyword(s):  
Southern California ◽  
Body Wave ◽  
Wave Spectrum ◽  
Local Network ◽  
Far Field ◽  
Local Magnitude ◽  
Magnitude Scales ◽  
Spectrum Measurements

abstract A necessary correction for relating local network magnitude scales to Richter's local magnitude (ML) involves accounting for the shape of the far-field body-wave spectrum of the phases used for determining magnitude. When not corrected for, this effect causes errors of about one magnitude unit at ML ∼ 3 for some southern California earthquakes. The discrepancy should be comparable for ML > 3, but at smaller magnitudes will decrease with decreasing ML. It may be corrected for either by direct comparison of network scales with magnitudes determined from Wood-Anderson seismograms, or by spectrum measurements over a range of magnitudes. The nature of the discrepancy and the corrections required to account for it are demonstrated by an example, the aftershocks of the 1968 Borrego Mountain, California earthquake.

scholarly journals Seismic investigations of the Martian near-surface at the InSight landing site

2020 ◽  
Author(s):  
Cedric Schmelzbach ◽  
Nienke Brinkman ◽  
David Sollberger ◽  
Sharon Kedar ◽  
Matthias Grott ◽  
...  
Keyword(s):  
Deep Structure ◽  
Landing Site ◽  
P Wave ◽  
Mission Design ◽  
Normal Operation ◽  
Seismic Signals ◽  
Martian Surface ◽  
Broadband Seismometer ◽  
Near Surface ◽  
Martian Regolith

<p>The InSight ultra-sensitive broadband seismometer package (SEIS) was installed on the Martian surface with the goal to study the seismicity on Mars and the deep interior of the Planet. A second surface-based instrument, the heat flow and physical properties package HP<sup>3</sup>, was placed on the Martian ground about 1.1 m away from SEIS. HP<sup>3</sup> includes a self-hammering probe called the ‘mole’ to measure the heat coming from Mars' interior at shallow depth to reveal the planet's thermal history. While SEIS was designed to study the deep structure of Mars, seismic signals such as the hammering ‘noise’ as well as ambient and other instrument-generated vibrations allow us to investigate the shallow subsurface. The resultant near-surface elastic property models provide additional information to interpret the SEIS data and allow extracting unique geotechnical information on the Martian regolith.</p><p>The seismic signals recorded during HP<sup>3</sup> mole operations provide information about the mole attitude and health as well as shed light on the near-surface, despite the fact that the HP<sup>3 </sup>mole continues to have difficulty penetrating below 40 cm (one mole length). The seismic investigation of the HP<sup>3</sup> hammering signals, however, was not originally planned during mission design and hence faced several technical challenges. For example, the anti-aliasing filters of the seismic-data acquisition chain were adapted when recording the mole hammering to allow recovering information above the nominal Nyquist frequency. In addition, the independently operating SEIS, HP<sup>3</sup> and lander clocks had to be correlated more frequently than in normal operation to enable high-precision timing.</p><p>To date, the analysis of the hammering signals allowed us to constrain the bulk P-wave velocity of the volume between the mole tip and SEIS (top 30 cm) to around 120 m/s. This low velocity value is compatible with laboratory tests performed on Martian regolith analogs with a density of around 1500 kg/m<sup>3</sup>. Furthermore, the SEIS leveling system resonances, seismic recordings of atmospheric pressure signals, HP<sup>3</sup> housekeeping data, and imagery provide additional constraints to establish a first seismic model of the shallow (topmost meters) subsurface at the landing site.</p>

Distributed Acoustic Sensing Using Dark Fiber for Array Detection of Regional Earthquakes

2021 ◽  
Author(s):  
Avinash Nayak ◽  
Jonathan Ajo-Franklin ◽  
Keyword(s):  
Urban Areas ◽  
Geothermal Field ◽  
Seismic Events ◽  
Broadband Seismometer ◽  
Acoustic Sensing ◽  
Array Detection ◽  
Distributed Acoustic Sensing ◽  
Back Azimuth ◽  
Ubiquitous Presence

Abstract The intrinsic array nature of distributed acoustic sensing (DAS) makes it suitable for applying beamforming techniques commonly used in traditional seismometer arrays for enhancing weak and coherent seismic phases from distant seismic events. We test the capacity of a dark-fiber DAS array in the Sacramento basin, northern California, to detect small earthquakes at The Geysers geothermal field, at a distance of ∼100  km from the DAS array, using beamforming. We use a slowness range appropriate for ∼0.5–1.0  Hz surface waves that are well recorded by the DAS array. To take advantage of the large aperture, we divide the ∼20  km DAS cable into eight subarrays of aperture ∼1.5–2.0  km each, and apply beamforming independently to each subarray using phase-weighted stacking. The presence of subarrays of different orientations provides some sensitivity to back azimuth. We apply a short-term average/long-term average detector to the beam at each subarray. Simultaneous detections over multiple subarrays, evaluated using a voting scheme, are inferred to be caused by the same earthquake, whereas false detections caused by anthropogenic noise are expected to be localized to one or two subarrays. Analyzing 45 days of continuous DAS data, we were able to detect all earthquakes with M≥2.4, while missing most of the smaller magnitude earthquakes, with no false detections due to seismic noise. In comparison, a single broadband seismometer co-located with the DAS array was unable to detect any earthquake of M<2.4, many of which were detected successfully by the DAS array. The seismometer also experienced a large number of false detections caused by spatially localized noise. We demonstrate that DAS has significant potential for local and regional detection of small seismic events using beamforming. The ubiquitous presence of dark fiber provides opportunities to extend remote earthquake monitoring to sparsely instrumented and urban areas.

Assessment of GRACE-FO Laser Ranging Interferometer measurements

2021 ◽  
Author(s):  
Athina Peidou ◽  
Felix Landerer ◽  
David Wiese ◽  
Matthias Ellmer ◽  
Eugene Fahnestock ◽  
...  
Keyword(s):  
High Frequency ◽  
Signal To Noise Ratio ◽  
Small Scale ◽  
Laser Ranging ◽  
High Signal ◽  
Measurement Sensitivity ◽  
One Year ◽  
Mass Transfers ◽  
Gravity Recovery ◽  
System Errors

<p>The performance of Gravity Recovery and Climate Experiment Follow‐On (GRACE-FO) laser ranging interferometer (LRI) system is assessed in both space and frequency domains. With LRI’s measurement sensitivity being as small as 0.05 nm/s<sup>2</sup> at GRACE-FO altitude we perform a thorough assessment on the ability of the instrument to detect real small-scale high-frequency gravity signals. Analysis of range acceleration measurements along the orbit for nearly one year of daily solutions suggests that LRI can detect signals induced by mass perturbation up to 26 mHz, i.e., ~145 km spatial resolution. Additionally, high frequency signals that are not adequately modeled by dealiasing models are clearly detected and their magnitude is shown to reach 2-3 nm/s<sup>2</sup>. The alternative K‐band microwave ranging system (KBR) is also examined and results demonstrate the inability of KBR to retrieve signals above 15mHz (i.e., shorter than ~200 km) as the noise of the KBR range acceleration increases rapidly. Overall, the first stream of LRI measurements shows that the high signal to noise ratio allows for detection of mass transfers in finer scales, however the ability to fully exploit the high-quality signal measured by the LRI in Level 2 products is still constrained by noise of background models and other onboard instrumentation and measurement system errors.</p><p>Copyright Acknowledgment: This work was performed at the California Institute of Technology's Jet Propulsion Laboratory under a contract with the National Aeronautics and Space Administration's Cryosphere Science Program.</p>

scholarly journals Analysis of Wheel Squeal and Flanging on Curved Railway Tracks

2019 ◽  
Vol 20 (12) ◽  
pp. 2077-2087 ◽  
Author(s):  
Jae Chul Kim ◽  
Yang Soo Yun ◽  
Hee-Min Noh
Keyword(s):  
Frequency Analysis ◽  
High Frequency ◽  
Railway Track ◽  
Railway Vehicle ◽  
Vertical Force ◽  
Railway Tracks ◽  
Noise Characteristics ◽  
Experimental Approaches ◽  
Curved Section ◽  
Natural Frequency Analysis

Abstract When a railway vehicle moves over a sharply curved section of track, intense high-frequency noises sometimes occur. These are potentially a source of annoyance to those living adjacent to railway tracks. To efficiently identify measures appropriate to reduce curve squeal, it is important to determine the dominant noise type. However, it is difficult to analyze the various noises made over curved sections of railway using general noise measurements. In this study, we analyzed squealing and flange noises using various experimental approaches. We first investigated the noise characteristics of the railway vehicle via structural analysis of the wheel. It was confirmed that a wheel has various natural frequencies and eigenmodes in the high frequency range, i.e. over 1000 Hz. A roller rig test was performed to measure and investigate the characteristics of the noise generated when an actual wheel and the curved section of the railway track come in contact with each other. In this experiment the squeal and the flange noises, in particular, were reproduced by adjustments made to the lateral angle and vertical force, respectively. Results confirmed that the squealing noise occurs in the high frequency region and the flange noise occurs in various modes. A study was also conducted to measure and analyze the noise in the actual curved section of an urban railway. By comparing the frequency analysis and the natural frequency analysis of the noise that was actually measured, the mode by which the wheel caused the squealing noise was confirmed. Furthermore, the influence of the noise generated inside and outside the curved section of the track was investigated based on velocity, and the influence of the former on the noise generated was also examined. This study provides information on the squeal and flange noises generated when a railway vehicle moves over a curved section of a railway using various experimental approaches.

Estimation of annual pollutant loadings in two small catchments and examination of their differences caused by regional properties

2006 ◽  
Vol 53 (2) ◽  
pp. 33-44 ◽  
Author(s):  
S. Fujii ◽  
M. Moriya ◽  
P. Songprasert ◽  
H. Ihara
Keyword(s):  
River Basin ◽  
High Frequency ◽  
Storm Event ◽  
Precipitation Pattern ◽  
Storm Events ◽  
Rainfall Events ◽  
Survey Results ◽  
One Year ◽  
Small Catchments

A series of runoff surveys was conducted for more than one year in two small catchments of the Kamo River basin (75.4 km2) and the Takano River basin (66.8 km2) in Kyoto, Japan, which adjoin each other, and may have the same precipitation pattern. The investigation consisted of a high-frequency periodic survey, a long-term regular survey and a storm event survey. The survey results were compared with the regional properties of the basins, and the following results were obtained. (1) Pollutant loadings were successfully estimated as two portions of base discharge and storm events discharge from the survey results. (2) Estimated annual loading of the sites was 2.9–4.5, 1.3–1.8, 17–27, 1.3–2.2, 0.076–0.97 t/km2/y, respectively for CODMn, DOC, SS, TN and TP. (3) 52–53% of the whole flow, which was caused by rainfall events, conveyed 81–87, 68–73, 92–95, 64–67, 76–81% of the whole loading, respectively for CODMn, DOC, SS, TN and TP. (4) Differences of regional properties in two basins cause different runoff patterns, but the differences in runoff patterns also depend on the rainfall patterns. In general, a more urbanized basin receives early and strong influence of precipitation on the storm event runoff.

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