scholarly journals PENELITIAN GAYABERAT DAN GEOMAGNIT KEPULAUAN ARU, CEKUNGAN WOKAM

2016 ◽  
Vol 12 (1) ◽  
pp. 1
Author(s):  
Tatang Patmawidjaya ◽  
Subagio Subagio
Keyword(s):  
Gravity Anomaly ◽  
Normal Fault ◽  
High Gravity ◽  
The South ◽  
Shallow Subsurface ◽  
The North ◽  
Residual Gravity Anomaly ◽  
Geomagnetic Anomaly ◽  
Geomagnetic Models ◽  
Geomagnetic Anomalies

Paparan Arafura di bagian selatan Kepulauan Aru merupakan depresi Lempeng Indo-Australia yang ditunjukkan oleh anomali gayaberat dan geomagnet tinggi. Sedangkan depresi di bagian utara yang tertahan Palung Aru diperlihatkan oleh anomali gayaberat tinggi dan anomali geomagnet rendah. Anomali ini diduga sebagai penebalan batuan metamorf yang mengalami pangangkatan sebagai alas cekungan Wokam. Analisis data gayaberat dan geomagnet mengindikasikan penurunan cekungan ini ke arah utara. Penurunan anomali gayaberat ke arah Pulau Wokam yang berarah baratdaya-timurlaut di selatan dan baratlaut-tenggara di daerah utara ditafsirkan sebagai struktur sesar. Hal ini dicirikan oleh arah sungai atau selat sebagai pemisah pulau-pulau di Kepulauan Aru. Anomali gayaberat residual mengindikasikan cekungan dan punggungan berarah baratdaya-timurlaut yang membentuk antiklin dan sinklin. Sesar dan lipatan ini menerus sebagai struktur geologi dangkal bawah permukaan. Berdasarkan pemodelan gayaberat dan geomagnet dapat dikatakan bahwa Cekungan Wokam cenderung menurun ke arah utara akibat sesar normal. Kata Kunci : gayaberat, geomagnet, pemodelan geologi, Cekungan Wokam Arafura Shelf in the southern part of the Aru Islands is a depression of the Indo-Australian crust at the south that indicated by high gravity and geomagnetic anomalies. While the northern depression blocked by the Aru Trough indicated by high gravity anomaly and low geomagnetic anomaly. These anomalies presumed as a thickening of the metamorphic rocks due to uplifting and acting as the basement of Wokam Basin. Gravity and geomagnetic analyses indicate a northward subsidence of the basin. The decreasing of the southwest–northeast gravity anomaly in the south and the northwest-southeast in the north, interpreted as a fault. It this characterized by the river direction or strait as islands separation in Aru Archipilagoes. Residual gravity anomaly indicates a southwest-northeast basin and ridge form anticline and syncline. These faults and folds are continuous as the shallow subsurface geological structures. On the base gravity and geomagnetic models, it can be concluded that Wokam Basin tends to subside northward as the result of a normal fault. Keywords: gravity, geomagnetic, geological models, Wokam Basin

scholarly journals Presence of interplate channel layer controls of slip during and after the 2011 Tohoku-Oki earthquake through the frictional characteristics

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ryoko Nakata ◽  
Takane Hori ◽  
Seiichi Miura ◽  
Ryota Hino
Keyword(s):  
Gravity Anomaly ◽  
Seismic Velocity ◽  
Seismic Survey ◽  
Japan Trench ◽  
Distribution Model ◽  
The South ◽  
Plate Interface ◽  
Residual Gravity ◽  
Channel Layer ◽  
Residual Gravity Anomaly

AbstractThere are significant differences between the middle and southern segments of the Japan Trench in terms of the seismic and aseismic slips on the plate interface and seismic velocity structures. Although the large coseismic slip of the 2011 Tohoku-Oki earthquake was limited to the middle segment, the observed negative residual gravity anomaly area in the southern segment corresponds to the postseismic slip area of the Tohoku-Oki earthquake. A density distribution model can explain the different slip behaviours of the two segments by considering their structural differences. The model indicates that the plate interface in the south was covered with a thick channel layer, as indicated by seismic survey imaging, and this layer resulted in a residual gravity anomaly. Numerical simulations which assumed evident frictional heterogeneity caused by the layer in the south efficiently reproduced M9 earthquakes recurring only in the middle, followed by evident postseismic slips in the south. This study proposes that although the layer makes the megathrust less compliant to seismic slip, it promotes aseismic slips following the growth of seismic slips on the fault in an adjacent region.

scholarly journals Gravity anomaly to identify Walanae fault using second vertical derivative method

2018 ◽  
Vol 2 (1) ◽  
pp. 34
Author(s):  
Marsellei Justia ◽  
Muhammad Fikri H Hiola ◽  
Nur Baiti Febryana S
Keyword(s):  
Gravity Data ◽  
Moving Average ◽  
Normal Fault ◽  
Reverse Fault ◽  
The South ◽  
Vertical Derivative ◽  
The North ◽  
Free Air ◽  
Free Air Anomaly ◽  
Fault Mechanism

<p class="Abstract">Research has been conducted to identify the Walanae Fault, coordinates 4–6 S and 118-120 E using anomalous gravity data. This research uses data measurement of Topography and the Free Air Anomaly from the TOPEX/Poseidon satellite. Then the authors processed to obtain the bouguer anomalies and made modeling by using the Surfer 10. The authors used the Second Vertical Derivative (SVD) with filter Elkins of Moving Average then analyze the graph of the SVD. The results shows the value of the residual anomaly in the north of fault is 25.21 mGal, in the middle occur range 17.67 mGal to 24.98 mGal and 30,376 mGal in the south of fault. The authors indicates the existence of a difference between the gravity between the Walanae Fault with surrounding geologic. From these results also show that Walanae Fault has a reverse fault mechanism in the northern part and the normal fault mechanism in the middle to the south, the authors conclude that the Walanae Fault is divided into two segments, that is the northern and the southern segment.</p>

Geodetic Investigation of the 30 October 2020 Mw 6.9 Samos-Izmir Earthquake

2021 ◽  
Author(s):  
Bilal Mutlu ◽  
Serdar Erol ◽  
Muhammed Raşit Çevikalp ◽  
Bihter Erol
Keyword(s):  
Normal Fault ◽  
The South ◽  
Online Processing ◽  
The North ◽  
North Side ◽  
Earthquake Research ◽  
Earthquake Research Institute ◽  
Gnss Network ◽  
Earthquake Zone ◽  
Gnss Data

&lt;p&gt;The earthquake with a magnitude of Mw 6.9 (according to Kandilli Observatory and Earthquake Research Institute-KOERI) occurred 8 km north of Samos Island at a depth of 16 km, on 30.10.2020, at 11:51:24 UTC. It took place on the north-dipping normal fault zone of approximately 40 km length in the sea between Samos Island of Greece and Ku&amp;#351;adas&amp;#305; Bay of Turkey. After the mainshock, a tsunami with the height exceeding 1 meter occurred in Seferihisar region, south of Izmir, and north side of Samos Island. In this study, a geodetic investigation of the Samos-Izmir earthquake using GNSS and SAR techniques was carried out. Within the scope of this study, 1Hz observations of Turkey National Continuous GNSS Network-Active (TUSAGA-Aktif) stations in the earthquake zone, were used, and it was aimed to reveal the co-seismic deformation caused by the earthquake. In addition to GNSS data, the InSAR process has been performed by using ESA Sentinel-1 SAR data, and the vertical deformations were clarified with the unwrapped interferogram. The GNSS data were processed using web-based online processing services according to the relative and absolute positioning techniques as static and kinematic modes. In conclusion, considering the absolute and relative static processing of pre- and post-earthquake GNSS data, the maximum horizontal deformations were observed at CESM and IZMI GNSS stations located in the north of the fault. Due to the earthquake, these points moved to the north direction and the maximum horizontal deformations were found as 5.5 cm and 3.5 cm, respectively. According to the kinematic processing of the GNSS data, instantaneous horizontal movements of 12 cm and 4 cm towards the north were observed at the same stations, respectively, at the time of the earthquake. On the contrary, DIDI and AYD1 GNSS stations, which are located in the south of the fault, moved to the south-east direction and the magnitude of horizontal deformations were smaller. Considering the InSAR results, it was seen a 10 cm uplift in the west of the island of Samos and a 10 cm subsidence at the northernmost part. Besides this, a 5 cm subsidence was observed in Izmir territory, the north side of the fault, by means of the interferogram.&lt;/p&gt;

scholarly journals STRONG SEISMIC EVENTS on the SOUTH-WESTERN FLANK of the BAIKAL RIFT in 2014: November 1, 2014, Кp=13.6, Mw=4.6, I0=7–8 URIK EARTHQUAKE and December 5, 2014, Кp=13.9, Mw=4.9, I0=7–8 HOVSGOL EARTHQUAKE

2020 ◽  
pp. 350-363
Author(s):  
V. Melnikova ◽  
N. Gileva ◽  
A. Seredkina ◽  
Ya. Radziminovich
Keyword(s):  
Normal Fault ◽  
Baikal Rift Zone ◽  
Strike Slip ◽  
Historical Seismicity ◽  
Seismic Events ◽  
The South ◽  
Moment Tensors ◽  
The North ◽  
Western Flank ◽  
Tectonic Position

We consider two earthquakes occurred at the south-western flank of the Baikal rift zone (BRZ): Urik, November 1, 2014 (Mwreg=4.6) and Hovsgol, December 5, 2014 (Mwreg=4.9). First of them is localized within the area of the Main Sayan fault, the second one is located at the north of the Hovsgol Lake. Seismic moment tensors (focal mechanisms, scalar seismic moments, moment magnitudes and hypocentral depths) of the study seismic events were calculated based on surface wave amplitude spectra. Earthquake hypocenters were found to be situated in the middle crust (h=14–21 km). Both events occurred under the strike-slip stress-strain field. The strike-slip was combined with a normal fault component in the source of the Urik earthquake and with a thrust fault component in the source of the Hovsgol earthquake. In both cases, shaking intensity in the nearest settlements (=42–124 km) was less than 4–5. Analysis of historical seismicity, seismological data on the Urik and Hovsgol earthquakes and the tectonic position of their sources demonstrates that the considered events are typical for the south-western flank of the BRZ and confirms the existence of the transition zone from rift structures at the central parts of the BRZ to regional compression structures in Northern Mongolia.

scholarly journals STUDI POTENSI MIGAS DENGAN METODE GAYABERAT DI LEPAS PANTAI UTARA JAKARTA

2016 ◽  
Vol 8 (1) ◽  
pp. 23
Author(s):  
Saultan Panjaitan ◽  
Nyoman Astawa
Keyword(s):  
Gravity Anomaly ◽  
Oil And Gas ◽  
Bouguer Anomaly ◽  
Normal Fault ◽  
Reservoir Rock ◽  
Reverse Fault ◽  
High Gravity ◽  
Low Gravity ◽  
Rock Density ◽  
Block Faulting

Anomali Bouguer dapat dibagi kedalam dua kelompok yaitu: Anomali gayaberat rendah terbentuk pada kisaran nilai 15 mGal hingga -40 mGal sebagai rendahan sinklin. Anomali gayaberat tinggi terbentuk pada kisaran nilai 40 mGal hingga 60 mGal sebagai tinggian antiklin. Formasi batuan dari atas hingga bawah sebagai berikut: Formasi Cisubuh rapat massa batuan 2.5 gr/cm³ ketebalan pada penampang ±1400 meter. Formasi Parigi rapat massa batuan 2.7 gr/cm³ ketebalan ± 400 meter. Formasi Cibulakan rapat massa batuan 2.6 gr/cm³ ketebalan ± 1600 meter. Formasi Jatibarang rapat massa 2.8 gr/cm³ ketebalan ± 1000 meter. Batuan reservoir didominasi lensa-lensa batupasir Formasi Cibulakan Atas, Cibulakan Bawah serta batugamping Formasi Parigi dan batupasir Formasi Talangakar. Batuan induk migas adalah serpih lakustrin halus Anggota Cibulakan Bawah (Formasi Talang Akar). Tinggian batuan reservoir pada anomali sisa antara 0 mGal hingga 16 mGal dan kedalaman pada penampang ± 1500 meter dengan rapat massa batuan 2.7 gr/cm³ Sesar normal terbentuk arah Utara-Selatan dan sesar naik arah Timur-Barat dikontrol oleh pematahan bongkah pada batuan alas metamorf dengan rapat massa 3.0 gr/cm³. Kata kunci: gayaberat, antiklin, anomali sisa, lepas pantai. Bouguer anomaly can be grouped into two parts: Low Gravity anomaly formed at 15 mGal to 40 mGal as syncline lower. High gravity anomaly formed at 40 mGal to 60 mGal as anticline high. Rock formation from the top to the bottom as follows: Cisubuh Formation rock of density with 2.5 gr / cm³ thickness at section of ± 1400 metre. Parigi Formation rock density of 2.7 gr / cm³ thicknees ± 400 metre. Cibulakan Formation density with 2.6 gr / cm³ thickness ± 1600 metre. Jatibarang Formation with density 2.8 gr / cm³ of thickness ± 1000 metre. Reservoir rock is dominated by lens of sandstone upper Cibulakan Formation, Lower Cibulakan and also Parigi Formation limestone and Talangakar Formation sandstone. Sourced rock of oil and gas from shales lacustrine of Cibulakan Lower or Talang Akar Formation. High Rocks reservoir at recidual anomaly range from 0 mGal to 16 mGal at section deepness ± 1500 metre with density of 2.7 gr / cm³, formed by normal fault of Northern-Southern direction and reverse fault Eastern-Western direction controlled by block faulting metamorphics bedrock with density of 3.0 gr / cm³. Keywords: gravity, anticline, recidual anomaly, offshore.

scholarly journals Interplate channel layer controls of slip during and after the 2011 Tohoku-Oki earthquake

2020 ◽  
Author(s):  
Ryoko Nakata ◽  
Takane Hori ◽  
Seiichi Miura ◽  
Ryota Hino
Keyword(s):  
Gravity Anomaly ◽  
Seismic Survey ◽  
Japan Trench ◽  
The South ◽  
Plate Interface ◽  
Seismic Slip ◽  
Residual Gravity ◽  
Channel Layer ◽  
Residual Gravity Anomaly ◽  
Postseismic Slip

Abstract There are remarkable differences between the middle and southern segments of the Japan Trench in terms of the seismic and aseismic slips on the plate interface and seismic velocity structures. The large coseismic slip of the 2011 Tohoku-Oki earthquake was limited to the middle segment, yet the observed negative residual gravity anomaly area in the southern segment corresponds to the postseismic slip area of the Tohoku-Oki earthquake. A model can explain the different slip behaviors of the two segments by considering their structural differences. The model indicated that the plate interface in the south was covered with a thick channel layer, as noted by seismic survey imaging, and this layer resulted in the residual gravity anomaly. Numerical simulations that assumed obvious frictional heterogeneity caused by the layer existing only in the south successfully reproduced M9 earthquakes recurring only in the middle, followed by evident postseismic slip in the south. We suggest that, while the layer makes the megathrust less compliant to seismic slip, it promotes aseismic slip following the growth of seismic slip on the fault in an adjacent region.

scholarly journals Constraining the geometry at depth of La Maladeta and Andorra-Mont Louis granites (Central Pyrenees) through gravity modelling

2020 ◽  
Author(s):  
Conxi Ayala ◽  
Pilar Clariana ◽  
Ruth Soto ◽  
Joan Martí ◽  
Aina Margalef ◽  
...  
Keyword(s):  
Gravity Anomaly ◽  
Cross Sections ◽  
Gravity Data ◽  
Gravity Modelling ◽  
The North ◽  
Geological Surveys ◽  
Residual Gravity Anomaly ◽  
Paleozoic Rocks ◽  
Subsurface Geometry ◽  
Central Pyrenees

&lt;p&gt;In the Central Pyrenees, where density contrast between the Paleozoic rocks and the intruded granitic bodies is measurable, geological cross-sections constrained with gravity data help to unravel the subsurface geometry of the granites.&lt;/p&gt;&lt;p&gt;With this goal in mind, during 2018 and 2019 several gravimetric surveys were carried out in the Central Pyrenees to improve the existent spatial resolution of the gravity data from the databases of the Spanish and Catalan Geological Surveys, especially in La Maladeta and Andorra Mont-Louis granites&amp;#8217; area. After the gravity reductions, we obtained the Bouguer gravity anomaly from which we calculated the residual gravity anomaly by subtracting a third degree polynomial which represents the regional anomaly in agreement with the geometry of the crust in this region.&lt;/p&gt;&lt;p&gt;The gravimetric response over La Maladeta and Andorra Mont-Louis granites is markedly dissimilar pointing out differences in the composition and geometry at depth of the two granites. La Maladeta granite shows a gravimetric zonation with small variations in its amplitude from one zone to the next, consistent with small lateral changes in its composition, predominantly granodioritic. By contrast, the Andorra Mont-Louis pluton is characterized by a relative minimum suggesting a more granitic composition.&lt;/p&gt;&lt;p&gt;With respect to the inferred geometry at depth, the results obtained from gravity modelling show that the La Maladeta granite displays a laccolithic shape with its basal contact deeping to the North whereas the Andorra Mont-Louis granite has a more batholitic shape. Although the emplacement age of both granites is similar (Late Carboniferous &amp;#8211; Early Permian), their different geometry at depth suggests that either (1) their emplacement mechanisms were different or (2) the subsequent Alpine orogeny affected both granites in different ways better preserving the original geometry of the Andorra Mont-Louis granite.&lt;/p&gt;

scholarly journals Development of surface ruptures by hanging-wall extension over a thrust ramp along the Ragged Mountain fault, Katalla, Alaska, USA: Applications of high-resolution three-dimensional terrain models

Geosphere ◽  
2021 ◽  
Author(s):  
Sarah N. Heinlein ◽  
Terry L. Pavlis ◽  
Ronald L. Bruhn
Keyword(s):  
High Resolution ◽  
Hanging Wall ◽  
Three Dimensional ◽  
Active Tectonics ◽  
Normal Fault ◽  
Fault Slip ◽  
The South ◽  
The North ◽  
Terrain Models ◽  
Surface Ruptures

High-resolution three-dimensional terrain models are used to evaluate the Ragged Mountain fault kinematics (Katalla, Alaska, USA). Previous studies have produced contradictory interpretations of the fault’s kinematics because surface ruptures along the fault are primarily steeply dipping, uphill-facing normal fault scarps. In this paper, we evaluate the hypothesis that these uphill-facing scarps represent extension above a buried thrust ramp. Detailed geomorphic mapping along the fault, using 20-cm-resolution aerial imagery draped onto a 1-m-resolution lidar (light detection and ranging) elevation model, was used to produce multiple topographic profiles. These profiles illustrate scarp geometries and prominent convex-upward topographic surfaces, indicating significant disturbance by active tectonics. A theoretical model is developed for fault-parallel flow over a thrust ramp that shows the geometric relationships between thrust displacement, upper-plate extension, and ramp dip. An important prediction of the model for this study is that the magnitude of upper-plate extension is comparable to, or greater than, the thrust displacement for ramps with dips greater than ~45°. This model is used to analyze profile shapes and surface displacements in Move software (Midland Valley Ltd.). Analyses of scarp heights allow estimates of hanging-wall extension, which we then use to estimate slip on the underlying thrust via the model. Assuming a low-angle (30°) uniformly dipping thrust and simple longitudinal extension via normal faulting, variations in extension along the fault would require a slip gradient from ~8 m in the north to ~22 m in the south. However, the same north-south variation in extension with a constant slip of 8–10 m may infer an increase in fault dip from ~30° in the north to ~60° in the south. This model prediction has broader implications for active-fault studies. Because the model quantifies relationships between hanging-wall extension, fault slip, and fault dip, it is possible to invert for fault slip in blind thrust ramps where hanging-wall extension is the primary surface manifestation. This study, together with results from the St. Elias Erosion and Tectonics Project (STEEP), clarifies the role of the Ragged Mountain fault as a contractional structure within a broadly sinistral shear system in the western syntaxis of the St. Elias orogeny.

Long-term Cyclic Variations of Prominences, Green and Red Coronae over Solar Cycles

2000 ◽  
Vol 179 ◽  
pp. 201-204
Author(s):  
Vojtech Rušin ◽  
Milan Minarovjech ◽  
Milan Rybanský
Keyword(s):  
Emission Lines ◽  
High Latitudes ◽  
Green Line ◽  
Solar Cycles ◽  
The South ◽  
Coronal Emission ◽  
Local Maxima ◽  
The North ◽  
Cyclic Variations

AbstractLong-term cyclic variations in the distribution of prominences and intensities of green (530.3 nm) and red (637.4 nm) coronal emission lines over solar cycles 18–23 are presented. Polar prominence branches will reach the poles at different epochs in cycle 23: the north branch at the beginning in 2002 and the south branch a year later (2003), respectively. The local maxima of intensities in the green line show both poleward- and equatorward-migrating branches. The poleward branches will reach the poles around cycle maxima like prominences, while the equatorward branches show a duration of 18 years and will end in cycle minima (2007). The red corona shows mostly equatorward branches. The possibility that these branches begin to develop at high latitudes in the preceding cycles cannot be excluded.

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