Hypocenter Relocation, Determination of Velocity Model and Correction Station in Gede Volcano for December 2017 Data

A nonlinear inversion method is presented, especially suited for the determination of global velocity models. In a certain sense, it can be considered as a generalization of methods based on traveltimes of reflections, with the requirement of accurately having to determine traveltimes replaced by the (less stringent and less subjective) requirement of having to define time windows around main reflections (or composite reflections) of interest. It is based on an error norm, related to the phase of the wavefield, which is directly computed from wavefield measurements. Therefore, the cumbersome step of interpreting arrivals and measuring arrival times is avoided. The method is applied to the reconstruction of a depth‐dependent global velocity model from a set of plane‐wave responses and is compared to other methods. Despite the fact that the new error norm only makes use of data having a temporal bandwidth of a few Hz, its behavior is very similar to the behavior of the error norm used in traveltime inversion.

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Magnitude Scales in Central Greece

Bulletin of the Geological Society of Greece ◽

10.12681/bgsg.16838 ◽

2018 ◽

Vol 40 (3) ◽

pp. 1114 ◽

Cited By ~ 1

Author(s):

G. Kaviris ◽

P. Papadimitriou ◽

K. Makropoulos

Keyword(s):

Goodness Of Fit ◽

Body Wave ◽

Velocity Model ◽

The Body ◽

Moment Magnitude ◽

Coefficient Of Determination ◽

Gulf Of Corinth ◽

Duration Magnitude ◽

The Moment

The Gulf of Corinth is one of the most active tectonic rifts around the world. Data used in the present study are obtained by the four digital stations of the Cornet Network which was installed in 1995 around the Eastern Gulf of Corinth. A velocity model was calculated, while the majority of local events were located within the Gulf of Corinth. Main scope of the study is the determination of a reliable earthquake magnitude. Concerning the duration magnitude Mo, a multiple linear regression technique was developed for the determination of the constants α, β and γ with very satisfactory values of errors. The coefficient of determination (goodness of fit) R2 was found equal to 0.99. Following, the moment magnitude Mw, which is considered to be the most reliable magnitude scale, was determined. Spectral analysis was applied for the calculation of the seismic moment M0 and a seismic catalogue was created. After the determination of the moment magnitude Mw and of the duration magnitude MD for the same dataset, a relationship between them was obtained, according to which Mw is systematically larger than Mjy Relationships between these magnitudes, the local magnitude ML and the body wave magnitude mb were also obtained.

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Determination of Earthquake Hypocenter Distribution using the Modified Joint Hypocenter Determination (MJHD) Method throughout the Palu-Koro Fault (Case Study: August-October, 2018)

IOP Conference Series Earth and Environmental Science ◽

10.1088/1755-1315/873/1/012074 ◽

2021 ◽

Vol 873 (1) ◽

pp. 012074

Author(s):

Dewi Ayu Swastika ◽

Harmita Lestari ◽

Aulia Puji Astuti ◽

Sabrianto Aswad ◽

Muhammad Fawzy Ismullah Massinai

Keyword(s):

Velocity Model ◽

Mean Value ◽

Time Data ◽

Tectonic Structures ◽

Hypocenter Determination ◽

Joint Hypocenter Determination ◽

Earthquake Hypocenter ◽

Earthquake Distribution ◽

Parameter Values

Abstract The area of Sulawesi, especially along the Palu Koro Fault, is an area that is largely influenced by the confluence and movement of plates as well as regional fault activity pathways with high levels of seismicity. Determining the location of the hypocenter accurately through relocation is required in identifying the detailed tectonic structures in the area. Relocation of the hypocenter using the Modified Joint Hypocenter Determination (MJHD) method using the IASP91 velocity model in the period August to October 2018 with the arrival time data from BMKG catalog. The results of hypocenter relocation using the MJHD method show that from 132 earthquake distribution points to 63 earthquake hypocenter points after the relocation. The change in the location of the hypocenter was much denser along the Palu Koro Fault route than before the relocation as evidenced by the mean value of rms (root mean square) before relocation was 1.31 and after relocation it became smaller (0.61). Changes in parameter values after relocation using the MJHD method caused the distribution of the earthquake hypocenter to be tighter towards the Palu Koro fault than before the relocation, where the distribution had a random and scattered pattern.

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Recent microseismicity observed at Hekla volcano and first velocity inversion results

10.5194/egusphere-egu2020-18954 ◽

2020 ◽

Author(s):

Martin Möllhoff ◽

Meysam Rezaeifar ◽

Christopher J. Bean ◽

Kristin S. Vogfjörd ◽

Bergur H. Bergsson ◽

...

Keyword(s):

Real Time ◽

Velocity Model ◽

Velocity Inversion ◽

The Real ◽

Location System ◽

Station Corrections ◽

High Hazard ◽

Real Time Detection ◽

Warning Time

<p>Hekla is one of the most active and dangerous volcanoes in Iceland presenting a high hazard to air travel and a growing tourist population. Until now the pre-eruption warning time at Hekla is only around one hour.&#160; In 2018 we installed the real-time seismic network HERSK directly on Hekla's edifice. If microseismicity on Hekla increases prior to the next eruption the network could possibly provide a means to improve early warning. In addition it is hoped that HERSK will better our understanding of the processes driving the evolution of pre-eruptive seismicity. The configuration and tuning of a dedicated real-time detection and location system requires the determination of a suitable velocity model and station corrections. We present a catalogue of recently detected local events that we use to invert for a 1-D velocity model. We observe significant variations in station corrections and conclude that it is important to account for these in the real-time detection and location system which we are developing based on the SeisComp3 software.</p>

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A new relationship between grain size and fall (settling) velocity in air

Progress in Physical Geography Earth and Environment ◽

10.1177/0309133314562442 ◽

2015 ◽

Vol 39 (3) ◽

pp. 361-387 ◽

Cited By ~ 9

Author(s):

Eugene J. Farrell ◽

Douglas J. Sherman

Keyword(s):

Grain Size ◽

Full Range ◽

Heuristic Method ◽

Strong Relationship ◽

Velocity Model ◽

Coefficient Of Determination ◽

Fall Velocity ◽

Natural Sand ◽

Considerable Uncertainty

The fall velocity of natural sand grains is a fundamental attribute of sediment transport in fluid environments where particles may become partially or fully suspended. Several formulae have been proposed to calculate the fall velocity of particles in air, but there is considerable uncertainty about which is the most accurate or appropriate for a given set of environmental conditions. Five experiments that reported observations of fall velocity of different types of particles in air are described, evaluated, and compared. The experiment data were quality-controlled using four criteria: (1) particles had to have sufficient drop heights to attain their terminal fall velocity; (2) particles had to be in the range of sand sizes; (3) data identified as being problematic by the original authors were removed; and (4) particles comprise natural, irregular shaped sediments. The quality-controlled data were aggregated and analyzed using linear regression to obtain a relationship between grain size ( d, in mm) and fall velocity ( w0, in ms-1): [Formula: see text]. This is a statistically strong relationship with a coefficient of determination of 0.89 ( p < 0.001). This relationship can be regarded as a universal fall velocity model for natural, sand-sized particles falling through a static column of air. In terms of predictive analyses, our heuristic method outperforms alternative formulae and yields a better fit to the experimental data over the full range of sand sizes.

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