scholarly journals Local seismotectonic analysis of the July 2019 Molucca Sea earthquake sequence based on moment tensor solutions

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Aditya Dwi Prasetio ◽  
Mohammad Hasib ◽  
Andi Amran ◽  
Syuhada ◽  
Febty Febriani ◽  
...  
Keyword(s):  
Moment Tensor ◽  
Normal Fault ◽  
Earthquake Sequence ◽  
Tectonic Activity ◽  
Waveform Data ◽  
Moment Tensor Solution ◽  
Compressional Stress ◽  
Fault Mechanism ◽  
Sea Area ◽  
Full Moment Tensor

AbstractWe investigate the local seismotectonic of the Molucca Sea area using moment tensor calculations for the earthquakes that occurred in July 2019 at a depth of 10–55 km. The mainshock of Mw 6.8 occurred on July 7, followed by aftershocks until July 18, with magnitudes ranging from Mw 4.6 to Mw 5.8. Moment tensor solutions are calculated by applying Isolated Asperities (ISOLA) software using the full waveform data recorded at regional seismic stations. The analyzed frequency bands used in this study are 0.01–0.03 Hz and 0.04–0.05 Hz for the event with Mw ≥ 5 and Mw < 5, respectively. We provide validations of new moment tensor solutions for Mw < 5 events in the Molucca Sea region for the period during the earthquake sequence. The results show that thrust and oblique faults are dominant during this event, which indicate a compressional stress of divergent double subduction (DDS) of the Sangihe and Halmahera arcs. Only one full moment tensor solution reveals the normal fault mechanism, which may indicate the manifestation of strain release of compressional stress in the surrounding area. Furthermore, these results also support the previous studies suggesting that the Talaud-Mayu Ridge located in the middle of the Molucca Sea has developed as a consequence of the transpressional tectonic activity.

gCAPjoint, A Software Package for Full Moment Tensor Inversion of Moderately Strong Earthquakes with Local and Teleseismic Waveforms

2020 ◽  
Vol 91 (6) ◽  
pp. 3550-3562
Author(s):  
Qipeng Bai ◽  
Sidao Ni ◽  
Risheng Chu ◽  
Zhe Jia
Keyword(s):  
Software Package ◽  
Epicentral Distance ◽  
Joint Inversion ◽  
Moment Tensor ◽  
Centroid Moment Tensor ◽  
Waveform Data ◽  
Strong Earthquakes ◽  
Moment Tensors ◽  
Seismic Networks ◽  
Full Moment Tensor

Abstract Earthquake moment tensors and focal depths are crucial to assessing seismic hazards and studying active tectonic and volcanic processes. Although less powerful than strong earthquakes (M 7+), moderately strong earthquakes (M 5–6.5) occur more frequently and extensively, which can cause severe damages in populated areas. The inversion of moment tensors is usually affected by insufficient local waveform data (epicentral distance &lt;5°) in sparse seismic networks. It would be necessary to combine local and teleseismic data (epicentral distance 30°–90°) for a joint inversion. In this study, we present the generalized cut-and-paste joint (gCAPjoint) algorithm to jointly invert full moment tensor and centroid depth with local and teleseismic broadband waveforms. To demonstrate the effectiveness and explore the limitations of this algorithm, we perform case studies on three earthquakes with different tectonic settings and source properties. Comparison of our results with global centroid moment tensor and other catalog solutions illustrates that both non-double-couple compositions of the focal mechanisms and centroid depths can be reliably recovered for very shallow (&lt;10  km) earthquakes and intermediate-depth events with this software package.

The 2020 Haenam earthquake sequence: The first observation of a seismic front on the Korean Peninsula migrating in a manner similar to fluid diffusion

2021 ◽  
Author(s):  
Minkyung Son ◽  
Chang Soo Cho ◽  
Jin-Hyuck Choi ◽  
Jeong-Soo Jeon ◽  
Yun Kyung Park
Keyword(s):  
Korean Peninsula ◽  
Fault Plane ◽  
Moment Tensor ◽  
Earthquake Swarm ◽  
Structural Data ◽  
Earthquake Sequence ◽  
Future Research ◽  
Permeability Barrier ◽  
Moment Tensor Solution ◽  
Fluid Diffusion

&lt;p&gt;Low-magnitude earthquakes (maximum Mw: 3.2) were recorded from late April 2020 onward in the county of Haenam, southwestern South Korea. Moderate to strong earthquakes had not previously been documented in instrumental, historical, or geological records. We identified 226 hypocentres in this earthquake sequence from April 25 to May 11, 2020. The seismic front of this sequence migrated in a manner similar to a diffusing fluid, with a hydraulic diffusivity of 0.012 m&lt;sup&gt;2&lt;/sup&gt;/s. This is the first observation of natural seismicity on the Korean Peninsula imitating fluid diffusion. We applied a cross-correlation approach to detect unrecorded events, and relocated the hypocentres of the 71 previously recorded and 155 newly detected events using data collected at permanent seismic stations; clear linearity was observed at the metre scale. Spatially, the hypocentres were distributed within a 0.3 km &amp;#215; 0.3 km fault plane at a depth of ~20 km, trending west-northwest&amp;#8211;east-southeast with a dip of ~70&amp;#176; in the south-southwestern direction. The moment tensor solution of the largest event had a strike of 98&amp;#176;, dip of 65&amp;#176;, and rake of 7&amp;#176;, which correspond to the fault geometry of the relocated hypocentres. The hypocentres progressed toward the upper eastern edge of the lineament. The largest event occurred at a shallow region of the fault plane, in the direction of hypocentre migration. Together, these results showed that the migration sequence of the 2020 Haenam earthquake mimicked the flow of a diffusing fluid. The structural data indicate that a fault&amp;#8211;fracture mesh geometry channelled fluid flow, supporting the concept of a &amp;#8220;fluid-driven earthquake swarm&amp;#8221; for the 2020 Haenam earthquake sequence. Regarding the final parts of the sequence, there appeared to be a second intrusion at the western end, and a permeability barrier at the eastern end, of the fault plane. The well-constrained hypocentre locations in our study provide essential data for future research, and our interpretations of hypocentre migration during this earthquake sequence may help to elucidate the mechanisms driving earthquake swarms under conditions of intraplate stress.&lt;/p&gt;

scholarly journals Pliocene to Quaternary tectonics in the Horná Nitra Depression (Western Carpathians)

2011 ◽  
Vol 62 (4) ◽  
pp. 381-393 ◽  
Author(s):  
Rastislav Vojtko ◽  
Juraj Beták ◽  
Jozef Hók ◽  
František Marko ◽  
Vojtech Gajdoš ◽  
...  
Keyword(s):  
Active Fault ◽  
Slip Rate ◽  
Normal Fault ◽  
Western Carpathians ◽  
Early Pleistocene ◽  
Tectonic Activity ◽  
Slip Rates ◽  
Compressional Stress ◽  
Mountain Front ◽  
Half Graben

Pliocene to Quaternary tectonics in the Horná Nitra Depression (Western Carpathians)The Horná Nitra Depression is an Upper Miocene-Quaternary intramontane sedimentary basin. This N-S elongated half-graben structure is rimmed from the west by the marginal Malá Magura fault which is the most distinctive fault in the Horná Nitra Depression, traditionally considered as an active fault during the neotectonic phase. This dislocation is attended by contrasting landforms and their parameters. The lowS-indexof about 1.10, at least two generations of well-preserved faceted slopes along this fault, and longitudinal river valley profiles point to the presence of a low-destructed actual mountain front line, which is typical for the Quaternary active fault systems. Comparison with known normal fault slip rates in the world makes it possible to set an approximate vertical slip rate between 0.3-1.1 m · kyr-1. The present-day fault activity is considered to be normal, steeply dipping towards the east according to structural and geophysical data. The NNW-SSE present-day tectonic maximum horizontal compressional stressSHand perpendicular minimum horizontal compressional stressShwas estimated in the Horná Nitra region. The Quaternary activity of the Malá Magura fault is characterized by irregular movement. Two stages of important tectonic activity along the fault were distinguished. The first stage was dated to the Early Pleistocene. The second stage of tectonic activity can by dated to the Late Pleistocene and Holocene. The Malá Magura fault is permeable for gases because the soil atmosphere above the ca. 150 meters wide fault zone contains increased contents of methane and radon.

A teleseismic body-wave analysis of the May 1980 Mammoth Lakes, California, earthquakes

1983 ◽  
Vol 73 (2) ◽  
pp. 419-434
Author(s):  
Jeffery S. Barker ◽  
Charles A. Langston
Keyword(s):  
Body Wave ◽  
Moment Tensor ◽  
Normal Fault ◽  
Strike Slip ◽  
Body Waves ◽  
P Wave ◽  
Moment Tensors ◽  
Double Couple ◽  
The Moment ◽  
Mammoth Lakes

abstract Teleseismic P-wave first motions for the M ≧ 6 earthquakes near Mammoth Lakes, California, are inconsistent with the vertical strike-slip mechanisms determined from local and regional P-wave first motions. Combining these data sets allows three possible mechanisms: a north-striking, east-dipping strike-slip fault; a NE-striking oblique fault; and a NNW-striking normal fault. Inversion of long-period teleseismic P and SH waves for the events of 25 May 1980 (1633 UTC) and 27 May 1980 (1450 UTC) yields moment tensors with large non-double-couple components. The moment tensor for the first event may be decomposed into a major double couple with strike = 18°, dip = 61°, and rake = −15°, and a minor double couple with strike = 303°, dip = 43°, and rake = 224°. A similar decomposition for the last event yields strike = 25°, dip = 65°, rake = −6°, and strike = 312°, dip = 37°, and rake = 232°. Although the inversions were performed on only a few teleseismic body waves, the radiation patterns of the moment tensors are consistent with most of the P-wave first motion polarities at local, regional, and teleseismic distances. The stress axes inferred from the moment tensors are consistent with N65°E extension determined by geodetic measurements by Savage et al. (1981). Seismic moments computed from the moment tensors are 1.87 × 1025 dyne-cm for the 25 May 1980 (1633 UTC) event and 1.03 × 1025 dyne-cm for the 27 May 1980 (1450 UTC) event. The non-double-couple aspect of the moment tensors and the inability to obtain a convergent solution for the 25 May 1980 (1944 UTC) event may indicate that the assumptions of a point source and plane-layered structure implicit in the moment tensor inversion are not entirely valid for the Mammoth Lakes earthquakes.

Identification of Tectonic Activity and Fault Mechanism From Morphological Signatures

2019 ◽  
pp. 99-123
Author(s):  
Arunima Nandy
Keyword(s):  
Active Zone ◽  
Satellite Images ◽  
Google Earth ◽  
Tectonic Activity ◽  
Landsat 8 ◽  
North East India ◽  
North East ◽  
Gis And Rs ◽  
Fault Mechanism ◽  
Tectonic Activities

Agartala, the capital of Tripura, is one of the most important and populated cities of North-East India. From the aspect of geomorphology, the whole area is characterized by highlands (tilla) and lowlands (lunga). Tectonically, Tripura falls under very active zone (Zone V). Assessment of tectonic activities of this region is very significant. For identification of tectonic activity, morphological or geomorphic signatures play very important role. The chapter identifies the presence of tectonic activity from morphological signatures in and around Agartala city. Landsat 8 OLI, maps from Geological Survey of India, Google Earth imageries have been used in this study. The presence of some lineaments and sag ponds has been identified on the basis of which fault mechanism of Agartala and Baramura hills has been delineated. This study contains a brief note on the conceptual demonstration of application of GIS and RS technologies and how morphological signatures and satellite images can help us to recognize tectonic activities over a region.

scholarly journals Automated full moment tensor inversion of coal mining-induced seismicity

2013 ◽  
Vol 195 (2) ◽  
pp. 1267-1281 ◽  
Author(s):  
Ali Tolga Sen ◽  
Simone Cesca ◽  
Monika Bischoff ◽  
Thomas Meier ◽  
Torsten Dahm
Keyword(s):  
Coal Mining ◽  
Induced Seismicity ◽  
Moment Tensor ◽  
Moment Tensor Inversion ◽  
Mining Induced Seismicity ◽  
Full Moment Tensor

THE ST. LAWRENCE VALLEY SYSTEM: A NORTH AMERICAN EQUIVALENT OF THE EAST AFRICAN RIFT VALLEY SYSTEM

1966 ◽  
Vol 3 (5) ◽  
pp. 639-658 ◽  
Author(s):  
P. S. Kumarapeli ◽  
V. A. Saull
Keyword(s):  
Fault Zone ◽  
Rift Valley ◽  
Continental Drift ◽  
Normal Fault ◽  
Tectonic Activity ◽  
Rift System ◽  
East African ◽  
Igneous Activity ◽  
Distinctive Type ◽  
African Rift

The St. Lawrence valley system (including the St. Lawrence, Ottawa, and Champlain valleys, and the St. Lawrence or Cabot trough) is coextensive with a well-defined pattern of seismic activity. The valley system is in a region of general updoming, normal faulting, and alkaline igneous activity of a distinctive type. The main phase of tectonic activity probably dates back to Mesozoic time. The above and other evidence presented in this paper indicate the existence of a major rift valley system that may be called the St. Lawrence rift system.The Rough Creek – Kentucky River fault zone, and the normal fault zones in Texas and Oklahoma, and the Lake Superior fault zone probably represent extensions of the St. Lawrence rift system. However, current seismicity indicates that the present tectonic activity is along a straight zone running through lakes Ontario and Erie into the Mississippi embayment. The St. Lawrence rift system may also be connected with the mid-Atlantic rift, in the region of the Azores plateau.The rift hypothesis presented may be useful as a regional guide in the search for niobium-bearing alkaline complexes and diamond-bearing kimberlites.Crustal tension in the St. Lawrence region may be genetically related to the opening of the Atlantic basin as postulated in the hypothesis of continental drift.

scholarly journals Μorphometric Analysis for the Assessment of Relative Tectonic Activity in Evia Island, Greece

Geosciences ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 264
Author(s):  
Kanella Valkanou ◽  
Efthimios Karymbalis ◽  
Dimitris Papanastassiou ◽  
Mauro Soldati ◽  
Christos Chalkias ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Fault Zone ◽  
Normal Fault ◽  
Morphometric Parameters ◽  
Tectonic Activity ◽  
Asymmetry Factor ◽  
Drainage Basins ◽  
Fault Systems ◽  
The North ◽  
Integrated Index

The aim of this study is to evaluate the relative tectonic activity in the north part of the Evia Island, located in Central Greece, and to investigate the contribution of neotectonic processes in the development of the fluvial landscape. Five morphometric parameters, including Drainage Basin Slope (Sb), Hypsometric Integral (Hi), Asymmetry Factor (Af), Relief Ratio (Rh), and Melton’s Ruggedness Number (M), were estimated for a total of 189 drainage basins. The catchments were classified into two groups, according to the estimated values of each morphometric parameter, and maps showing their spatial distribution were produced. The combination of the calculated morphometric parameters led to a new single integrated Index of relative tectonic activity (named Irta). Following this indexing, the basins were characterized as of low, moderate, or high relative tectonic activity. The quantitative analysis showed that the development of the present drainage systems and the geometry of the basins of the study area have been influenced by the tectonic uplift caused by the activity of two NW-SE trending offshore active normal fault systems: the north Gulf of Evia fault zone (Kandili-Telethrion) and the Aegean Sea fault zone (Dirfis), respectively. The spatial distribution of the values of the new integrated index Irta showed significant differences among the drainage basins that reflect differences in relative tectonic activity related to their location with regard to the normal fault systems of the study area.

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