Automatic interpretation of regional short period seismic signals using CUSUM-SA algorithms

Satellite gravimetry observations from GRACE (Gravity Recovery and Climate Experiment) and GRACE Follow-On are widely used to study the co-seismic and post-seismic deformations caused by large earthquakes. Temporal gravity changes from GRACE provide good constraints to investigate the fault slips of large earthquakes especially for oceanic areas. However, reliable retrieval of seismic signals is still challenging due to large uncertainties and limited spatial and temporal resolutions of GRACE observations. To extract the co- and post-seismic signals from GRACE, the time series fitting method based on least squares is commonly used. In the time series fitting, the earthquake occurrence time parameter (t0) is usually set at the mid-month point, since most available GRACE time-variable data are monthly solutions. Nevertheless, a lot of large earthquakes did not occur exactly at mid-month. By simulative tests, we demonstrate that the commonly used mid-month approximation for the fitting parameter t0 can cause noticeable bias for the seismic signal extraction. The several-days deviation in the parameter t0 leads to obvious difference for the time series fitting of seismic signals, since the post-seismic changes are rapid and significant within a short period after the earthquake. With the case study of the 2004 Mw9.1 Sumatra-Andaman earthquake (which occurred on December 26), we indicate that the bias due to the commonly used mid-month t0 approximation reaches above 10 percent amplitude of the extracted co-seismic signals. Thus the exact date for the fitting parameter t0 should be used for more reliable separation of the co- and post-seismic signals from GRACE observations.

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Overview of observed seismic signals on Mars

10.5194/egusphere-egu2020-19482 ◽

2020 ◽

Author(s):

Savas Ceylan ◽

John F. Clinton ◽

Domenico Giardini ◽

Maren Böse ◽

Martin van Driel ◽

...

Keyword(s):

Energy Content ◽

Low Frequency ◽

Careful Analysis ◽

Atmospheric Effects ◽

Seismic Signals ◽

S Wave ◽

Ground Segment ◽

Short Period ◽

Data Content ◽

Set Up

InSight landed on Mars in late November 2018, and the SEIS package, which consists of one short period and one very broadband sensor, was deployed on the surface shortly after. The data returned by the InSight is monitored in a timely manner by the Marsquake Service (MQS), a ground segment support group of InSight that has been set up to establish and maintain the seismicity catalogue. The MQS has at least one member on duty who routinely checks the data for any type of seismic signals. All suspicious signals are then communicated to the InSight team after evaluation.To date, MQS has identified more than 365 events which are classified into two general families as high and low frequency, with each family having unique features in terms of their energy content. The most distinct quakes detected so far belong to the low frequency family that occurred on Sol 173 and 235, and have clear P and S-wave arrivals that reveal a distance around 30 degrees east of the lander, pointing the region in the vicinity of Cerberus Fossae. In addition to the signals of seismic origin, the SEIS data contain features that originate from other sources such as atmospheric effects or electronics. Part of these non-seismic observations may resemble quakes which may lead to wrong interpretations, and therefore require careful analysis.Here, we show examples of signals of both seismic and non-seismic origins. We describe the characteristics of these observations in time and frequency domains in order to give an overview of martian data content.

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Auditory discrimination of seismic signals from earthquakes and explosions

Bulletin of the Seismological Society of America ◽

10.1785/bssa0550010001 ◽

1965 ◽

Vol 55 (1) ◽

pp. 1-25

Author(s):

G. E. Frantti ◽

L. A. Levereault

Keyword(s):

Auditory System ◽

Seismic Data ◽

Magnetic Tape ◽

Path Length ◽

World Wide ◽

Propagation Path ◽

Seismic Signals ◽

Chance Performance ◽

Short Period ◽

Seismic Frequencies

Abstract Magnetic tape recordings of short-period seismic signals from approximately 200 earthquakes and explosions were time-compressed by a factor of up to 512 to shift seismic frequencies to the audible range. These seismic data include the inhomogeneities introduced by substantial variations in the locations of sources and receivers (world-wide), propagation path length (32 to 7000 km), and source magnitude (M = 0.5 to M = 6.5). Subjects were trained with a representative set of the “seismic sounds.” Auditory experiments were conducted to determine the ability of the human auditory system to distinguish between seismic signals from earthquakes and explosions. The results of the experiments suggest that a trained listener can identify approximately two-thirds of the seismic sounds presented, where one half corresponds to chance performance.

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Seismic classification of rainfall-induced lahars at Volcán de Colima, México

10.5194/egusphere-egu21-13348 ◽

2021 ◽

Author(s):

Ivonne Martínez Valdés ◽

Víctor Hugo Márquez Ramírez ◽

Lucia Capra ◽

Velio Coviello ◽

Raúl Arámbula Mendoza

Keyword(s):

Broad Band ◽

Correlation Method ◽

Active Volcano ◽

Video Camera ◽

Liquid Composition ◽

Seismic Signals ◽

Linear Discriminant ◽

Video Images ◽

Seismic Sensors ◽

Short Period

Rainfall-induced lahars are one of the most common phenomena in tropical volcanoes. Volc&#225;n de Colima (VdC) is the most active volcano in Mexico regarding intra-eruptive lahar generation. Lahars represent one of the main hazards for local communities located within a radius of 15 km from the summit. During the rainy season, from May to October dozens of lahars occur in the different ravines draining the VdC. Since 2007, lahar monitoring is performed for both research and civil purposes. Rain gauges, seismic sensors, cameras, and infrasound sensors are part of the current monitoring system deployed at Montegrande ravine (MR) which is located in the southern flank of the volcano. Here we present the data collected during the 2018 monitoring season that are composed of seventeen flow events, six of which feature the most complete dataset ever collected at MR. Data are recorded with multiple stations including broad-band seismic sensors (120 s), geophones (4.5 Hz), short-period seismometers (1 Hz) and a video camera installed along a 1.5 km channel reach. Three types of lahars have been classified based on the join-analysis of seismic signals and video images of these latter six events: dry front, diluted and multi-front. These classes are related to the solid-liquid composition and dynamics of the flows, and to the rainfall amount possibly triggering the processes. A linear discriminant analysis (LDA) is proposed to classify the rest of the events using seismic and rainfall records. Preliminary results show how the flow velocity and the presence of coarse fronts, inferred by means of cross-correlation method and inspection of the video images respectively, are the first factors controlling the characteristics of the seismic signals. This work also demonstrate how seismic techniques represent a valuable tool to describe the remarkable variability of flow dynamics along the travel path.&#160;

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Seismic signals preceding the explosive eruption of Mount St. Helens, Washington, on 18 May 1980

Bulletin of the Seismological Society of America ◽

10.1785/bssa07306a1797 ◽

1983 ◽

Vol 73 (6A) ◽

pp. 1797-1813

Author(s):

Anthony Qamar ◽

William St. Lawrence ◽

Johnnie N. Moore ◽

George Kendrick

Keyword(s):

Seismic Waves ◽

Low Frequency ◽

Seismic Energy ◽

B Value ◽

Volcanic Earthquake ◽

Seismic Signals ◽

Volcanic Earthquakes ◽

Short Period ◽

Stressed Region ◽

Mount St Helens

Abstract The intense seismic activity which preceded the 18 May 1980 eruption of Mount St. Helens, Washington, released 2 to 3 × 1018 ergs/day in earthquakes that did not correlate temporally with phreatic eruptions which occurred during the same period. Although the b value and amplitude ratios (long-period/short-period) of the earthquakes vary with time, there are no definitive precursors to the 18 May earthquake and eruption. A Mogi type II frequency-magnitude relation, with critical magnitude Mc = 4.6, constrains the characteristic dimension of the highly stressed region under Mount St. Helens to approximately 3 km, preceding the eruption. A major increase in seismic energy release and a decrease in b value around 1 April 1980 may indicate the first major influx of magma into the upper portion of the volcano. Seismic waves from low-frequency volcanic earthquake have large periods at all epicentral distances. Recordings of volcanic earthquakes from 2 to 4 April 1980 at sites 4 to 9 km from Mount St. Helens show two predominant periods of 0.55 and 1.0 sec. We speculate that seismic signals from the low-frequency volcanic earthquakes have a tectonic origin, but may be modified by pressure oscillations in nearby magma.

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Note on use of a Sofar geophone to determine seismicity of regional oceanic areas

Bulletin of the Seismological Society of America ◽

10.1785/bssa0520030689 ◽

1962 ◽

Vol 52 (3) ◽

pp. 689-691

Author(s):

D. H. Shurbet

Keyword(s):

Ocean Bottom ◽

Seismic Signals ◽

Regional Seismicity ◽

Short Period

abstract Daily Bermuda short period seismograms are compared with Sofar geophone records for a period of three years. Many short-period seismic signals were recorded on the geophone record that are not on the seismograms. Therefore, it is suggested that a geophone array could be most useful in determining regional seismicity in oceanic areas. The large number of geophone signals recorded gives some indication that the advantages of the expected quiet of the ocean bottom may be somewhat offset.

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Seismology of the Oso-Steelhead landslide

Natural Hazards and Earth System Sciences Discussions ◽

10.5194/nhessd-2-7309-2014 ◽

2014 ◽

Vol 2 (12) ◽

pp. 7309-7327 ◽

Cited By ~ 5

Author(s):

C. Hibert ◽

C. P. Stark ◽

G. Ekström

Keyword(s):

Surface Waves ◽

Slope Failure ◽

Source Parameters ◽

Seismic Energy ◽

Seismic Signals ◽

Period Analysis ◽

Long Period ◽

Landslide Volume ◽

Short Period ◽

Seismic Records

Abstract. We carry out a combined analysis of the short- and long-period seismic signals generated by the devastating Oso-Steelhead landslide that occurred on 22 March 2014. The seismic records show that the Oso-Steelhead landslide was not a single slope failure, but a succession of multiple failures distinguished by two major collapses that occurred approximately three minutes apart. The first generated long-period surface waves that were recorded at several proximal stations. We invert these long-period signals for the forces acting at the source, and obtain estimates of the first failure runout and kinematics, as well as its mass after calibration against the mass-center displacement estimated from remote-sensing imagery. Short-period analysis of both events suggests that the source dynamics of the second are more complex than the first. No distinct long-period surface waves were recorded for the second failure, which prevents inversion for its source parameters. However, by comparing the seismic energy of the short-period waves generated by both events we are able to estimate the volume of the second. Our analysis suggests that the volume of the second failure is about 15–30% of the total landslide volume, which is in agreement with ground observations.

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Broadband, short-period or geophone nodes? Quality assessment of Passive Seismic signals acquired during the Maupasacq experiment

First Break ◽

10.3997/1365-2397.n0085 ◽

2018 ◽

Vol 36 (4) ◽

pp. 71-76 ◽

Cited By ~ 3

Author(s):

K. Polychronopoulou ◽

A. Lois ◽

N. Martakis ◽

S. Chevrot ◽

M. Sylvander ◽

...

Keyword(s):

Quality Assessment ◽

Seismic Signals ◽

Short Period ◽

Passive Seismic

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Identification and characterization of rockfalls using seismic signals, LiDAR, and imagery. Advances on real-time detection

10.5194/egusphere-egu21-13149 ◽

2021 ◽

Author(s):

Bixen Telletxea ◽

Mar Tapia ◽

Marta Guinau ◽

Manuel J. Royán ◽

Pere Roig Lafon ◽

...

Keyword(s):

Real Time ◽

Automatic Detection ◽

Early Warning Systems ◽

Seismic Attenuation ◽

Small Scale ◽

Seismic Signals ◽

Seismic Sensors ◽

Short Period ◽

Real Time Detection

Seismic sensors installed in areas prone to rockfalls provide a continuous record of the phenomenon, allowing real-time detection and characterization. Detection of small scale rockfalls (< 0.001 m3), that might be precursors of larger events, can be worthwhile for early warning systems of rockfalls. However, seismic signals are closely dependent on the characteristics of the event and on the geotechnical characteristics of the ground, making the detection of small rockfalls complex and requiring detailed in-situ analyzes. For this reason, an experiment was carried out on the UB experimental site (Puigcerc&#243;s Cliff, Catalonia, NE Spain) on 6th-7th of June 2013, where 21 rocks with volumes ranging from 0.0015 m3 to 0.0004 m3 were thrown from the top of the cliff (200 m long and 27 m high) and the seismic signals were registered with three 3D short period seismic sensors located at different distances from the rock wall: 57 m, 67 m, and 107 m.The recorded seismic signals have a frequency content between 10-30 Hz, and the duration of the peak amplitudes varied between 0.3 and 0.6 s. Based on these characteristics, different phases of the dynamics of the rockfalls were identified, including main impacts, rebounds, flights, rolling and final stop of the events. The furthest station recorded the lowest frequency and amplitude values, limiting our ability to detect those blocks smaller than 0.0015 m3. Comparing the results with the nearest station, seismic attenuation phenomena is detectable even at distances of 50 m.After the experiment, a permanent seismic station was installed in the area, at 107 m from the cliff. Using LiDAR and 2D imagery monitoring, two naturally triggered rockfalls were identified on 30th and 31st August 2017 (0.28 m3 and 0.25 m3 respectively). Based on the results from the experiment and an automatic detection system, these main events and prior minor events have been found in the continuous seismic records of this permanent station. The characteristics of these natural detachments differ partially from the artificially triggered rockfalls during the experiment, since the geometry of the seismic signals is different. The observed shapes of the natural detachments are similar to that of granular flows, much more continuous than the sharp shapes that were observed in the isolated blocks of the experiment. This shows the possibility of incorporating seismic stations for the automatic detection and initial characterization of rockfalls and its effectiveness in detecting frequencies of occurrence.In order to evaluate the possibility of estimating rockfall volumes, diverse energy ratios (Es/Ep) were calculated. However, precise volume estimation is not possible. Nevertheless, the combination of seismic data with LiDAR and photographic techniques allows accurate new volume calculations of rockfalls to be incorporated progressively into the study of rockfalls.ACKNOWLEDGMENTS: The authors would like to acknowledge the financial support from CHARMA (CGL2013-40828-R) and PROMONTEC (CGL2017-84720-R AEI/FEDER, UE) projects, Spanish MINEICO. We are also thankful to Origens UNESCO Global Geopark.

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Seismic signatures of atmospheric disturbances in the Western Pacific as a tool for reconstruction of their dynamics

Geofísica Internacional ◽

10.22201/igeof.00167169p.2021.60.4.2124 ◽

2021 ◽

Vol 60 (4) ◽

pp. 333-356

Author(s):

Vyacheslav Zobin

Keyword(s):

Cold Front ◽

Spectral Characteristics ◽

Tropical Storm ◽

Seismic Signals ◽

Frequency Range ◽

Power Spectral ◽

Atmospheric Disturbances ◽

Short Period ◽

The One ◽

Two Stages

The wind and products of snowfalls and rainfalls touching the ground generate the seismic signals. During the decades, the study of seismic signatures of atmospheric disturbances, cyclones, was based on analysis of the ambient seismic noise in the low-frequency range which allowed identification of cyclones and location of the storm position. The methodology of monitoring of the atmospheric events using the short-period seismic signals recorded by a sensor installed at a height of about 4 km above sea level at the summit of dormant volcano Nevado de Colima is proposed. The methodology includes the indication of the seismic signatures of atmospheric disturbances on the daily helicorder displays of seismic signals with following analysis of waveforms, produced by the impact of rainfalls and snowfalls with the ground surface, and their Fourier spectral characteristics. Then, the reconstruction of the passage of the atmospheric events, based on the power spectral densities of the one-hour seismic records, which is performed mutually with the satellite observations. The methodology was applied to study the passage of hurricane Dora and its preceding tropical storm (June 2017) and the cold front system number 25 (January 2018). There were indicated the periods of actions of tropical storm, hurricane, and two stages of the cold front on the helicorder images. Then the characteristic waveforms for each period were selected. Analysis of the spectral characteristics of these waveforms demonstrated that the rainfalls, occurring during the tropical storm, hurricane and the initial stage of the cold front passage, generated the seismic signals within the frequency range between 1.0-1.8 Hz while the snowfall during the second stage of the cold front passage generated the seismic signals within the frequency range between 2.6 and 3.7 Hz. The reconstruction of dynamics of the passage of the atmospheric events based on the power spectral densities of the one-hour seismic records allowed to see the comparable intensity of tropical storm and hurricane, and two stages of the cold front. These results demonstrate a possibility for monitoring the passage of atmospheric disturbances in real time or to perform the reconstruction the dynamics of these events during past time using the short-period seismic signals recorded at the high heights.

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