Magnitude Scales for Marsquakes Calibrated from InSight 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.

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Updated Magnitude Scales for Mars

10.5194/egusphere-egu2020-13034 ◽

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

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 B&#246;se 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.

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Mechanisms Associated with Large Daily Rainfall Events in Northeast Brazil

Journal of Climate ◽

10.1175/2010jcli3457.1 ◽

2011 ◽

Vol 24 (2) ◽

pp. 376-396 ◽

Cited By ~ 16

Author(s):

Brant Liebmann ◽

George N. Kiladis ◽

Dave Allured ◽

Carolina S. Vera ◽

Charles Jones ◽

...

Keyword(s):

Daily Rainfall ◽

Annual Rainfall ◽

Northeast Brazil ◽

Kelvin Wave ◽

Rainfall Events ◽

Independent Events ◽

Precipitation Anomalies ◽

Wave Trains ◽

Using Data ◽

Forcing Mechanisms

Abstract The mechanisms resulting in large daily rainfall events in Northeast Brazil are analyzed using data filtering to exclude periods longer than 30 days. Composites of circulation fields that include all independent events do not reveal any obvious forcing mechanisms as multiple patterns contribute to Northeast Brazil precipitation variability. To isolate coherent patterns, subsets of events are selected based on anomalies that precede the Northeast Brazil precipitation events at different locations. The results indicate that at 10°S, 40°W, the area of lowest annual rainfall in Brazil, precipitation occurs mainly in association with trailing midlatitude synoptic wave trains originating in either hemisphere. Closer to the equator at 5°S, 37.5°W, an additional convection precursor is found to the west, with a spatial structure consistent with that of a Kelvin wave. Although these two sites are located within only several hundred kilometers of each other and the midlatitude patterns that induce precipitation appear to be quite similar, the dates on which large precipitation anomalies occur at each location are almost entirely independent, pointing to separate forcing mechanisms.

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

Bulletin of the Seismological Society of America ◽

10.1785/bssa0630010315 ◽

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.

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Retrieval of source-extent parameters and the interpretation of corner frequency

Bulletin of the Seismological Society of America ◽

10.1785/bssa07306a1499 ◽

1983 ◽

Vol 73 (6A) ◽

pp. 1499-1511

Author(s):

Paul Silver

Keyword(s):

Body Wave ◽

Amplitude Spectrum ◽

Low Frequency ◽

P Wave ◽

Corner Frequency ◽

S Wave ◽

Dislocation Source ◽

Statistical Measures ◽

Dislocation Models ◽

Planar Dislocation

Abstract A method is proposed for retrieving source-extent parameters from far-field body-wave data. At low frequency, the normalized P- or S-wave displacement amplitude spectrum can be approximated by |Ω^(r^,ω)| = 1 − τ2(r^)ω2/2 where r^ specifies a point on the focal sphere. For planar dislocation sources, τ2(r^) is linearly related to statistical measures of source dimension, source duration, and directivity. τ2(r^) can be measured as the curvature of |Ω^(r^,ω)| at ω = 0 or the variance of the pulse Ω^(r^,t). The quantity ωc=2τ−1(r^) is contrasted with the traditional corner frequency ω0, defined as the frequency at the intersection of the low- and high-frequency trends of |Ω^(r^,ω)|. For dislocation models without directivity, ωc(P) ≧ ωc(S) for any r^. A mean corner frequency defined by averaging τ2(r^) over the focal sphere, ω¯c=2<τ2(r^)>−1/2, satisfies ωc(P) > ωc(S) for any dislocation source. This behavior is not shared by ω0. It is shown that ω0 is most sensitive to critical times in the rupture history of the source, whereas ωc is determined by the basic parameters of source extent. Evidence is presented that ωc is the corner frequency measured on actual seismograms. Thus, the commonly observed corner frequency shift (P-wave corner greater than the S-wave corner), now viewed as a shift in ωc is simply a result of spatial finiteness and is expected to be a property of any dislocation source. As a result, the shift cannot be used as a criterion for rejecting particular dislocation models.

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

10.5194/egusphere-egu2020-20481 ◽

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

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 HP3, was placed on the Martian ground about 1.1 m away from SEIS. HP3 includes a self-hammering probe called the &#8216;mole&#8217; 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 &#8216;noise&#8217; 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.The seismic signals recorded during HP3 mole operations provide information about the mole attitude and health as well as shed light on the near-surface, despite the fact that the HP3 mole continues to have difficulty penetrating below 40 cm (one mole length). The seismic investigation of the HP3 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, HP3 and lander clocks had to be correlated more frequently than in normal operation to enable high-precision timing.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/m3. Furthermore, the SEIS leveling system resonances, seismic recordings of atmospheric pressure signals, HP3 housekeeping data, and imagery provide additional constraints to establish a first seismic model of the shallow (topmost meters) subsurface at the landing site.

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Noise Issues of Concrete-Pavement Texturing

Transportation Research Record Journal of the Transportation Research Board ◽

10.3141/1702-09 ◽

2000 ◽

Vol 1702 (1) ◽

pp. 69-79 ◽

Cited By ~ 6

Author(s):

John R. Jaeckel ◽

David A. Kuemmel ◽

Yosef Z. Becker ◽

Alex Satanovsky ◽

Ronald C. Sonntag

Keyword(s):

Second Phase ◽

Department Of Transportation ◽

Portland Cement Concrete ◽

Noise Levels ◽

The Road ◽

Wisconsin Department ◽

Noise Characteristics ◽

Texture Parameters ◽

Noise Measurements ◽

Using Data

The second phase of a project researching the texture and noise characteristics of portland cement concrete (PCC) pavements was sponsored by the Wisconsin Department of Transportation and FHWA. The team of Marquette University and HNTB Corporation measured and analyzed the noise and texture parameters of 57 test sites in Colorado, Iowa, Michigan, Minnesota, North Dakota, and Wisconsin. Conclusions pertaining to tire-and-pavement noise were drawn using data from several types of acoustical tests, including objective noise measurements (exterior and interior), subjective noise evaluations, and a prominent frequency analysis. Texture parameters of all test sites were measured with the road surface analyzer (ROSAN). ROSAN texture measurements proved invaluable in analyzing why different textures exhibited different noise characteristics. Both uniform and random transverse tining provide higher interior and exterior noise levels than skewed or longitudinal tining. Transverse tining, even in some random-spaced textures, can cause a discrete frequency or whine. As the depth and width of tining increased, so did the noise levels. Randomly spaced patterns are sensitive to spacing. Ground PCC pavement exhibited no discrete frequencies. Recommendations include the need for better quality control over tining and a wet-pavement-accident study of longitudinal tining. If noise considerations are paramount, longitudinal tining is recommended. If texture is paramount, skewed tining is recommended. If a skew is not possible, then carefully constructed random transverse is recommended.

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3D elastic full-waveform inversion of surface waves in the presence of irregular topography using an envelope-based misfit function

Geophysics ◽

10.1190/geo2017-0081.1 ◽

2018 ◽

Vol 83 (1) ◽

pp. R1-R11 ◽

Cited By ~ 24

Author(s):

Dmitry Borisov ◽

Ryan Modrak ◽

Fuchun Gao ◽

Jeroen Tromp

Keyword(s):

Surface Wave ◽

Objective Function ◽

Surface Waves ◽

Large Scale ◽

Body Wave ◽

Waveform Inversion ◽

Full Waveform Inversion ◽

S Wave ◽

Near Surface ◽

Full Waveform

Full-waveform inversion (FWI) is a powerful method for estimating the earth’s material properties. We demonstrate that surface-wave-driven FWI is well-suited to recovering near-surface structures and effective at providing S-wave speed starting models for use in conventional body-wave FWI. Using a synthetic example based on the SEG Advanced Modeling phase II foothills model, we started with an envelope-based objective function to invert for shallow large-scale heterogeneities. Then we used a waveform-difference objective function to obtain a higher-resolution model. To accurately model surface waves in the presence of complex tomography, we used a spectral-element wave-propagation solver. Envelope misfit functions are found to be effective at minimizing cycle-skipping issues in surface-wave inversions, and surface waves themselves are found to be useful for constraining complex near-surface features.

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Shear-coupled higher mode seismic surface waves

Bulletin of the Seismological Society of America ◽

10.1785/bssa0570010001 ◽

1967 ◽

Vol 57 (1) ◽

pp. 1-8 ◽

Cited By ~ 1

Author(s):

Stuart Crampin

Keyword(s):

Surface Waves ◽

Wave Motion ◽

S Wave ◽

Higher Modes ◽

Mode Wave ◽

Mode Dispersion ◽

Seismic Surface Waves ◽

Wave Trains ◽

Group Velocities

abstract Some higher mode wave trains with irregular dispersion, and some anomalies in the S-wave motion at epicentral distances less than 30°, are shown to be shear-coupled higher modes. The group velocities along the higher mode portions of the paths agree well with observations of direct higher mode dispersion in Scandinavia.

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Regional propagation characteristics and source parameters of earthquakes in northeastern North America

Bulletin of the Seismological Society of America ◽

10.1785/bssa0840010001 ◽

1994 ◽

Vol 84 (1) ◽

pp. 1-15 ◽

Cited By ~ 1

Author(s):

John Boatwright

Keyword(s):

Site Response ◽

Source Parameters ◽

Low Frequency ◽

Response Spectra ◽

Spectral Shape ◽

Propagation Characteristics ◽

S Wave ◽

Data Set ◽

Wave Trains ◽

Source Site

Abstract The vertical components of the S wave trains recorded on the Eastern Canadian Telemetered Network (ECTN) from 1980 through 1990 have been spectrally analyzed for source, site, and propagation characteristics. The data set comprises some 1033 recordings of 97 earthquakes whose magnitudes range from M ≈ 3 to 6. The epicentral distances range from 15 to 1000 km, with most of the data set recorded at distances from 200 to 800 km. The recorded S wave trains contain the phases S, SmS, Sn, and Lg and are sampled using windows that increase with distance; the acceleration spectra were analyzed from 1.0 to 10 Hz. To separate the source, site, and propagation characteristics, an inversion for the earthquake corner frequencies, low-frequency levels, and average attenuation parameters is alternated with a regression of residuals onto the set of stations and a grid of 14 distances ranging from 25 to 1000 km. The iteration between these two parts of the inversion converges in about 60 steps. The average attenuation parameters obtained from the inversion were Q = 1997 ± 10 and γ = 0.998 ± 0.003. The most pronounced variation from this average attenuation is a marked deamplification of more than a factor of 2 at 63 km and 2 Hz, which shallows with increasing frequency and increasing distance out to 200 km. The site-response spectra obtained for the ECTN stations are generally flat. The source spectral shape assumed in this inversion provides an adequate spectral model for the smaller events (Mo < 3 × 1021 dyne-cm) in the data set, whose Brune stress drops range from 5 to 150 bars. For the five events in the data set with Mo ≧ 1023 dyne-cm, however, the source spectra obtained by regressing the residuals suggest that an ω2 spectrum is an inadequate model for the spectral shape. In particular, the corner frequencies for most of these large events appear to be split, so that the spectra exhibit an intermediate behavior (where |ü(ω)| is roughly proportional to ω).

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The ROMY project: A 4-component ring laser for geophysics and geodesy

10.5194/egusphere-egu2020-7381 ◽

2020 ◽

Author(s):

Heiner Igel ◽

Felix Bernauer ◽

Joachim Wassermann ◽

Shihao Yuan ◽

Andre Gebauer ◽

...

Keyword(s):

Ground Motion ◽

Ring Laser ◽

High Sensitivity ◽

Point Of View ◽

Small Scale ◽

Broadband Seismometer ◽

Rotational Ground Motion ◽

Noise Characteristics ◽

The Individual ◽

Redundant Component

The ROMY ring laser was constructed with 4 non-orthogonal triangular-shaped cavities of 12 m side length in the Geophysical Observatory outside Munich, Germany, in 2016. The large dimensions of the individual rings have the benefit of allowing high sensitivity surpassing in principle the sensitivity of the G-ring at the Fundamentalstation Wettzell. However, the concrete construction of ROMY is geometrically less stable than the G-ring that is built on a rigid Xerodur plate. Each of the four rings has its own Sagnac frequency. The horizontal triangular ring laser at the top of the inverted tetrahedral ROMY structure allows direct comparison of teleseismic signals and noise with the G-ring at a distance of 200km. It also serves as redundant component. In principle, three orthogonal components of rotational ground motion can be obtained by linear combination from any combination of three rings, that - due to the variable Sagnac frequency - have different noise characteristics. We report on the behavior and observations of ROMY from a seismological point of view. It is fair to say that ROMY provides the most accurate direct 3-component rotational ground motion seismic observations to date. In combination with a collocated broadband seismometer as well as a surrounding small-scale seismic array, we analyse regional, teleseismic events, and ocean-generated noise and compare with array-derived rotation.

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