scholarly journals RELOKASI HIPOSENTER GEMPABUMI MENGGUNAKAN METODE MODIFIED JOINT HYPOCENTER DETERMINATION (MJHD) UNTUK ANALISIS ZONA SUBDUKSI SUMATERA BAGIAN SELATAN

2020 ◽  
Vol 4 (1) ◽  
pp. 49-63
Author(s):  
Deswita Sari ◽  
Fadiah Khairina ◽  
Gatut Daniarsyad
Keyword(s):  
Subduction Zone ◽  
Arrival Time ◽  
Tectonic Setting ◽  
P Wave ◽  
S Wave ◽  
Tectonic Plates ◽  
Hypocenter Determination ◽  
Joint Hypocenter Determination ◽  
Earthquake Hypocenter ◽  
Hypocenter Relocation

The part of south Sumatera is very vulnerable region in case of earthquake disaster caused by convergent boundary of two tectonic plates Indo-Australian Plates and Eurasian Plates. Precise hypocenter analysis is needed to understand about  the accurate tectonic setting such as subduction zone in the area. Hypocenter relocation is used to recalculate earthquake hypocenter to become more accurate. To produce a more accurate hyposenter this hyposenter relocation is done by using the method of Modified Joint Hypocenter Determination (MJHD). Relocation using the Modified Joint Hypocenter Determination (MJHD) method uses IASP91 wave velocity which assumes that the inner structures are heterogeneous. In this study, used data P-wave and S-wave  arrival time in the period January 2010 s.d December 2016 with coordinates -3.5º s.d -9º LS - 99º s.d 106.5º BT. The results of the relocation using MJHD showed a change of earthquake hypocenter shown by RMS (Root Mean Square) value ranging from 0.2 s.d 0.5. There are three subduction of the part in south sumatra. The subduction zone formed in Bengkulu is about 26.78º, the subduction zone of Lampung is around 30.225º and the subduction of the Sunda Strait is about 52.53º. Subduction zone of Bengkulu at depth of 250 km, Lampung and Sunda Strait at depth 400 km.

Joint microseismic event location and anisotropic velocity inversion with the cross double-difference method using downhole microseismic data

Geophysics ◽  
2020 ◽  
Vol 85 (3) ◽  
pp. KS63-KS73
Author(s):  
Yangyang Ma ◽  
Congcong Yuan ◽  
Jie Zhang
Keyword(s):  
Arrival Time ◽  
Velocity Model ◽  
P Wave ◽  
Double Difference ◽  
S Wave ◽  
Arrival Times ◽  
Monitoring Well ◽  
The Cross ◽  
Microseismic Event ◽  
Wave Arrival

We have applied the cross double-difference (CDD) method to simultaneously determine the microseismic event locations and five Thomsen parameters in vertically layered transversely isotropic media using data from a single vertical monitoring well. Different from the double-difference (DD) method, the CDD method uses the cross-traveltime difference between the S-wave arrival time of one event and the P-wave arrival time of another event. The CDD method can improve the accuracy of the absolute locations and maintain the accuracy of the relative locations because it contains more absolute information than the DD method. We calculate the arrival times of the qP, qSV, and SH waves with a horizontal slowness shooting algorithm. The sensitivities of the arrival times with respect to the five Thomsen parameters are derived using the slowness components. The derivations are analytical, without any weak anisotropic approximation. The input data include the cross-differential traveltimes and absolute arrival times, providing better constraints on the anisotropic parameters and event locations. The synthetic example indicates that the method can produce better event locations and anisotropic velocity model. We apply this method to the field data set acquired from a single vertical monitoring well during a hydraulic fracturing process. We further validate the anisotropic velocity model and microseismic event locations by comparing the modeled and observed waveforms. The observed S-wave splitting also supports the inverted anisotropic results.

Microstructural, compositional and petrophysical properties of mylonitic granodiorites from an extensional shear zone (Rhodope Core complex, Greece)

2014 ◽  
Vol 151 (6) ◽  
pp. 1051-1071 ◽  
Author(s):  
ROSALDA PUNTURO ◽  
ROSOLINO CIRRINCIONE ◽  
EUGENIO FAZIO ◽  
PATRIZIA FIANNACCA ◽  
HARTMUT KERN ◽  
...  
Keyword(s):  
Shear Zone ◽  
Seismic Anisotropy ◽  
Eastern Mediterranean ◽  
Tectonic Setting ◽  
P Wave ◽  
S Wave ◽  
Southern Boundary ◽  
Foliation Plane ◽  
Wave Velocities ◽  
Progressive Strain

AbstractAt the southern boundary of the Rhodope Massif, NE Greece, the Kavala Shear Zone (KSZ) represents an example of the Eastern Mediterranean deep-seated extensional tectonic setting. During Miocene time, extensional deformation favoured syntectonic emplacement and subsequent exhumation of plutonic bodies. This paper deals with the strain-related changes in macroscopic, geochemical and microstructural properties of the lithotypes collected along the KSZ, comprising granitoids from the pluton, aplitic dykes and host rock gneisses. Moreover, we investigated the evolution of seismic anisotropy on a suite of granitoid mylonites as a result of progressive strain. Isotropic compressional and shear wave velocities (Vp,Vs) and densities calculated from modal proportions and single-crystal elastic properties at given pressure–temperature (P–T) conditions are compared to respective experimental data including the directional dependence (anisotropy) of wave velocities. Compared to the calculated isotropic velocities, which are similar for all of the investigated mylonites (average values:Vp~ 5.87 km s−1,Vs~ 3.4 km s−1,Vp/Vs= 1.73 and density = 2.65 g cm−3), the seismic measurements give evidence for marked P-wave velocity anisotropy up to 6.92% (at 400 MPa) in the most deformed rock due to marked microstructural changes with progressive strain, as highlighted by the alignment of mica, chlorite minerals and quartz ribbons. The highest P- and S-wave velocities are parallel to the foliation plane and lowest normal to the foliation plane. Importantly,Vpremains constant within the foliation with progressive strain, but decreases normal to foliation. The potential of the observed seismic anisotropy of the KSZ mylonites with respect to detectable seismic reflections is briefly discussed.

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

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.

scholarly journals Hypocenter Determination of Volcano-Tectonic (VT) Earthquake around Agung Volcano in Period October-December 2017 Using a Non-Linear Location Method: A Preliminary Result

2021 ◽  
Vol 873 (1) ◽  
pp. 012098
Author(s):  
P P Rahsetyo ◽  
D P Sahara ◽  
A D Nugraha ◽  
D K Syahbana ◽  
Zulfakriza ◽  
...  
Keyword(s):  
Volcanic Eruptions ◽  
Velocity Model ◽  
P Wave ◽  
Significant Activity ◽  
S Wave ◽  
Location Method ◽  
Hypocenter Determination ◽  
Velocity Models ◽  
Central Java ◽  
Non Linear

Abstract Agung is one of active volcanoes in Indonesia, located on island of Bali. Since 1963, Agung has not had significant activity, until in September 2017 the volcano was active again which was marked by increased seismic activity and eruptions in November 2017. Therefore, to analyze the dynamics and processes of active volcanic eruptions requires an understanding of the structure of the volcano, especially the position of the magma reservoir and its path. The depiction of the structure of this volcano can be analyzed by determining the location of the earthquake due to volcanic activity, especially Volcano-Tectonic (VT) earthquake. In this study, we determined the location of the hypocenter around the Agung using the non-linear location method. VT earthquakes have similar characteristics to tectonic earthquakes so this method can be used to determine the initial hypocenter. The data used in this study came from 8 PVMBG seismographs from October to December 2017. We manually picking arrival time of P- and S-waves from the 3948 VT events found. Pair of P and S wave phases with 18741 P-wave phases and 17237 S-wave phases, plotted in a wadati diagram resulting in a vp/vs ratio of 1.7117. We use 1D velocity models derived from Koulakov with the assumption that the geology of the study area is not much different from the volcanoes in Central Java. The resulting hypocenter distribution shows a very random location and has uncertain X, Y, and Z directions from a range of 0 to 91 km. This study limits this uncertainty to 5 km resulting in a more reliable earthquakes distribution of 3050 events. The results indicate 2 clustered events, a swarm of VT events that occur every month at a depth of 8 to 15 km and there are 2 paths that lead to the top of Agung and SW of that swarm. These preliminary results will be used to update 1D velocity model and relocate the events beneath Agung region for further studies.

The Conditional Contributions of Electromagnetism and QED To Natural Hazards in Both Nano and Macro Cosmic Scales

2020 ◽  
Author(s):  
Taner Sengor
Keyword(s):  
Natural Hazards ◽  
Van Der Waals ◽  
Vertical Direction ◽  
P Wave ◽  
Secondary Wave ◽  
S Wave ◽  
Geophysical Research ◽  
Tectonic Plates ◽  
The Earth ◽  
Qed Effects

<p>The Earth itself with its inwards and outwards is a unique and complete system according to all events effecting the Earth<sup>1</sup>. All the natural events involving hazards are the results of self-controlling mechanism of the complex network of this unique system. Several contributions and reports presented this fact. The classical approaches trying to explain earthquake events, say EQs, and related phenomena may be taken as approximations working for the EQs less than 5.9 Richter in magnitude according to observations coming from the application of this approach. The EQs bigger than 5.9 Richter involve very different ingredients given with dynamics based on the gravity in classical geophysics<sup>1</sup>. The ranges of (5.9+n, 5.9+n+1) for every n=1, 2, 3, ... present different formulations due to validity of the approximations and orders of the variables as relative to the energy density and frequency levels.  The fact in here comes with the compactness coming with the electromagnetically equivalent models<sup>1</sup>.</p><p> </p><p>The planetary movements effect both the mechanics and dynamics of tectonic plates like tidal action of Pascal’s law modified with stochastic interactions. The Earth’s plates may move and collide with each other due to the forces generated by these displacements. The Primary wave comes from these mechanics of plates under planetary effects, tidal effects, and/or effects of extended Pascal’s and Archimedes’ principles for compressible liquids involving non-adiabatic gasses in semi-open containers. All these effects are effective in vertical direction, totally. P wave is a result of these forces generated by the dynamics of collision of plate-to-plate, plate-to-sea, plate-to-ocean, and/or plate-to-tidal processes coming from planetary motions and acts between plates. Secondary wave come from the effects of Casimir-Polder forces and Van der Waals potentials generated by the nano-displacements occurring among touch-to-touch phases of plates just at the end of P wave phases. These QED effects are effective in horizontal direction in total iff they can generate an EQ. If the plates touch to each other with the effect of forces coming from P wave then this induces Van der Waals potentials and forces like Casimir-Polder force work on the plates generating big amount of energy then big EQs can come to truth. It is possible to model the P wave phases with the deterministic ingredients and processes; however, modelling the S wave phases are not possible without stochastic ingredients and processes. The processes like storms, typhoon, etc. developing with the atmospheric events generate the similar effects. The waves coming with EQs propagate in inflective trajectories; therefore, these waves propagate in inflective spaces. This analysis illustrates the gravity interactions of the Earth with other planets generating electromagnetic interactions in both nano-scale and quantum level in Earth’s interior as the actual trigger of EQs. The excessive fall works like the insurance for EQs preventing the occurrence of significant EQs and so, reducing the huge damage arriving from significant and/or bigger EQs.</p><p>-------------------</p><p><sup>1</sup>Sengor T, “The Globally Compact Multi-Network of the Earth: the self-controlling mechanisms in natural hazards above significant level,” Geophysical Research Abstracts, Vol. 21, EGU2019-17127,2019, General Assembly 2019.</p>

scholarly journals S WAVE VELOCITY STRUCTURE IN NONTECTONIC SE ASIA BY SEISMOGRAM ANALYSIS OF THE EARTHQUAKES IN SUMATRA–JAVA AT TATO STATION, TAIWAN

2010 ◽  
Vol 04 (03) ◽  
pp. 181-195
Author(s):  
BAGUS JAYA SANTOSA
Keyword(s):  
East Asia ◽  
Subduction Zone ◽  
Wave Velocity ◽  
Upper Mantle ◽  
Arrival Time ◽  
Velocity Structure ◽  
Synthetic Seismogram ◽  
Earth Model ◽  
South East Asia ◽  
S Wave

The S wave velocity structure beneath South-East Asia and South China Sea due to earthquakes in Sumatra–Java subduction zone has been investigated through seismogram analysis in time domain and three components simultaneously, using data recorded in TATO, Taiwan seismological station. The synthetic seismogram was calculated using the GEMINI method, which consists of the earth model and the CMT solution of the earthquake. A low-pass filter with corner frequency of 20 mHz is imposed to the seismograms. Response file inversion subjected on the measured seismogram will compare the measured and the synthetic seismogram in the same unit. The seismogram comparison indicated that the synthetic seismogram constructed from PREMAN earth model deviates greatly from the measured one. The deviation occurred on the arrival time of surface wave of Rayleigh and Love as well as S body waves. The S, Love, and Rayleigh waveform deviations on arrival time or oscillation number are solved by changing the gradient of βh into positive in the upper mantle layers, and corrections for zero-order coefficients of β speed polynomial in every earth mantle layers. The interpretation results of seismogram analysis using waveform comparison indicate that the nontectonic South-East Asia area in front of subduction zone has strong negative correction of βv in the upper mantle and with smaller factor also at earth layers below. This result shows stronger vertical anisotropy than that indicated by the PREMAN earth model.

A synthetic 2-D-elastic full-waveform inversion study for the Ecuadorian margin—resolution capability of a dense onshore/offshore network

2020 ◽  
Vol 222 (2) ◽  
pp. 1236-1244
Author(s):  
L Gassner ◽  
N Thiel ◽  
A Rietbrock
Keyword(s):  
Subduction Zone ◽  
Waveform Inversion ◽  
Wave Model ◽  
P Wave ◽  
Full Waveform Inversion ◽  
S Wave ◽  
Traveltime Tomography ◽  
Full Waveform ◽  
Local Earthquake ◽  
Source Orientation

SUMMARY Subduction zones are the places on the Earth where the greatest earthquakes occur. It is now widely accepted that seismic asperities at the interface of subducting plates play a major role in whether a region of a subduction zone behaves seismically, creating strong earthquakes or exhibits aseismic slip. In the last decades, huge advances have been made to decipher the underlying processes; however, the physical parameters along the subduction zone interfaces are still not very well known due to a sparsity of high-resolution experiments and significant costs associated with amphibious seismic experiments. Therefore, synthetic tests are needed to investigate the potential of currently possible high density seismic deployments and to aid future experiment design. As standard local earthquake traveltime tomography in a subduction zone setting cannot resolve structures on a kilometre scale at depth, we explore the suitability of full-waveform inversion (FWI) to increase resolution by using amplitude and phase information in the recorded earthquake seismograms. We apply 2-D-elastic FWI to synthetic earthquake data, using vertical and horizontal receivers, and utilize a realistic model of the seismic velocities at the Ecuadorian margin. We add perturbations within the subducting plates of 4×4 km and 2×2 km in P- and S-wave velocities, respectively, such that potential crosstalk between the two models can be identified. Our results show that the location and amplitude of the perturbations can be reconstructed in high quality down to approximately 70 km depth. We find that the inversion of the S-wave velocity prior to the inversion of the P-wave velocity is necessary to guarantee a good reconstruction of both models; however, the spatial resolution of the S-wave model is superior to the P-wave model. We also show that frequencies up to 1 Hz are sufficient to achieve high resolution. Further tests demonstrate how results depend on the accuracy of the estimated source orientation. Resulting models do not suffer in quality as artefacts near the source positions compensate for the inaccuracy of source orientation. If sources are located within the subducted plate instead of beneath, resulting models are comparable and the convergence of the inversion scheme is sped up. The accuracy of the source position within the model compared to the true earthquake location is critical and implies that earthquake relocation during the inversion process is necessary, in a similar way as in local earthquake traveltime tomography.

Lattice preferred orientation and seismic anisotropy of chloritoid in subduction zone

2021 ◽  
Author(s):  
Jungjin Lee ◽  
Mainak Mookherjee ◽  
Taehwan Kim ◽  
Haemyeong Jung ◽  
Reiner Klemd
Keyword(s):  
Subduction Zone ◽  
Subduction Zones ◽  
Seismic Anisotropy ◽  
Elastic Anisotropy ◽  
P Wave ◽  
Stability Field ◽  
S Wave ◽  
P Waves ◽  
Hydrous Minerals ◽  
Natural Rock

<p>Subduction zones are often characterized by the presence of strong trench-parallel seismic anisotropy and large delay times. Hydrous minerals, owing to their large elastic anisotropy and strong lattice preferred orientations (LPOs) are often invoked to explain these observations. However, the elasticity and LPO of chloritoid, which is one such hydrous phases relevant in subduction zone settings, is poorly understood. In this study, we measured the LPO of polycrystalline chloritoid in natural rock samples and obtained the LPO-induced seismic anisotropy and evaluated the thermodynamic stability field of chloritoid in subduction zones. The LPO of chloritoid aggregates displayed a strong alignment of the [001] axes subnormal to the rock foliation, with a girdle distribution of the [100] axes and the (010) poles subparallel to the foliation. New elasticity data of single-crystal chloritoid showed a strong elastic anisotropy of chloritoid with 47% for S-waves (V<sub>S</sub>) and 22% for P-waves (V<sub>P</sub>), respectively. The combination of the LPO and the elastic anisotropy of the chloritoid aggregates produced a strong S-wave anisotropy of AV<sub>S</sub> = 18% and a P-wave anisotropy of AV<sub>P</sub> = 10%. Our results indicate that the strong LPO of chloritoid along the hydrated slab-mantle interface and in subducting slabs can influence trench-parallel seismic anisotropy in subduction zones with “cold” geotherms.</p>

scholarly journals Preliminary Results of Double Difference Tomography at Sunda-Banda Arc

2021 ◽  
Vol 873 (1) ◽  
pp. 012067
Author(s):  
Haolia ◽  
M. I. Sulaiman ◽  
P. T. Brilianti ◽  
R. P. Nugroho ◽  
I. Madrinovella ◽  
...  
Keyword(s):  
Tectonic Setting ◽  
Active Volcano ◽  
P Wave ◽  
Double Difference ◽  
Benioff Zone ◽  
Good Resolution ◽  
S Wave ◽  
Low Velocity ◽  
The North ◽  
Banda Arc

Abstract The Sunda-Arc transition to the Banda Arc is located on the south of the Flores Island, Indonesia, where the Australian lithosphere is moving to the north direction. On-going subduction process dictates the tectonic setting though some studies also suggest a collision and obduction may occur in the past due to of plate buoyancy. This area has active seismicity with frequent large magnitude events. To better understand the tectonic system in this region, we performed double-difference tomography inversion using regional events. We obtained the data catalog from the Indonesian Agency of Meteorology, Climatology, and Geophysics ranging from 116° to 125° east longitude and -6.5° to 12.5° latitude. We collected 4312 events data, detected from 15 stations from January 2015 to December 2019. Final relocated hypocenters showed a reduced fixed-depth problem and a more clustered event, although some deep events disappear. Most events are related to the subducting Benioff zone with some clustered events in the northern area may be related to back-arc thrust. We also observed clustered events near active volcano region and reduced shallow seismicity region to the west of the Timor Island. Resolution test using the checkerboard and Derivative weigh Sum (DWS) shows that fair P wave resolution can be achieved until 300 km, although a smearing start to show at a deeper depth. However, due to lack of arrival S wave data, the resolution test suggest good resolution can only be seen until a depth of 100 km. Tomogram P and S wave models show a clear dipping subducting slab from south to North down to a 250 km. We also spot a fast velocity band near the Timor Island area that similar to the previous tomography study, interpreted as sliver forearm. We spotted a band of lower Vp, lower Vs and higher Vp/Vs at shallow depth close to the volcanic line and we interpreted this as a zone of higher temperature, that may relate to magmatic activity in this region. We also noticed a zone of low velocity and higher Vp/Vs that may relate with dehydration and partial melting. However, we feel this still uncertain due to low Vs resolution.

Automatic algorithm for triaxial hodogram source location in downhole acoustic emission measurement

Geophysics ◽  
1989 ◽  
Vol 54 (4) ◽  
pp. 508-513 ◽  
Author(s):  
K. Nagano ◽  
H. Niitsuma ◽  
N. Chubachi
Keyword(s):  
Acoustic Emission ◽  
Arrival Time ◽  
Field Measurements ◽  
Source Location ◽  
P Wave ◽  
Likelihood Method ◽  
Emission Measurement ◽  
Wave Direction ◽  
S Wave ◽  
Wave Arrival

An automatic acoustic emission (AE) source location algorithm has been developed for downhole AE measurement of subsurface cracks by using the triaxial hodogram method. The P-wave arrival time is detected by analyzing crosscorrelation coefficients among three components of AE signal energy; the P-wave direction is determined by the method of least squares. For detection of S-wave arrival time, a maximum‐likelihood method analyzes a distribution of instantaneous values of the SH-wave component amplitude. This algorithm can locate an AE source as accurately as human analysis. For field measurements, it takes less than 4 s to locate an AE source using a 16-bit personal computer with a program in C language. Automatic AE source location by the triaxial hodogram method has been realized with this algorithm.

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