A transient in surface motions dominated by deep afterslip subsequent to a shallow supershear earthquake: the 2018 Mw 7.5 Palu case.

2021 ◽  
Author(s):  
Nicolai Nijholt ◽  
Wim Simons ◽  
Joni Efendi ◽  
Dina Sarsito ◽  
Riccardo Riva
Keyword(s):  
Physical Mechanism ◽  
Fault Plane ◽  
Strike Slip ◽  
Fault Rupture ◽  
Seismic Rupture ◽  
Rupture Plane ◽  
Elastic Rebound ◽  
Slip Event ◽  
Seismic Deformation ◽  
Locked Fault

<div> <div> <div> <p>The 2018 <em>M<sub>w</sub></em> 7.5 Palu earthquake is a remarkable strike-slip event due to its nature as a shallow supershear fault rupture across several segments and a destructive tsunami that followed co-seismic deformation. GPS offsets in the wake of the 2018 earthquake display a transient in the surface motions of northwest Sulawesi. A Bayesian approach identifies (predominantly a-seismic) deep afterslip on and below the co-seismic rupture plane as the dominant physical mechanism causing the cumulative, post-seismic, surface displacements whereas viscous relaxation of the lower crust and poro-elastic rebound contribute negligibly. We confirm a correlation between shallow supershear rupture and post-seismic surface transients with afterslip activity in the zone below an inter-seismically locked fault plane where the slip rate tapers from zero to creeping.</p> </div> </div> </div>

scholarly journals The rate of Seismic deformation in the Gulf of Aqaba as inferred from moment tensor summation

2020 ◽  
Author(s):  
Sattam Almadani
Keyword(s):  
Shear Deformation ◽  
Fault Plane ◽  
Moment Tensor ◽  
Strike Slip ◽  
Gulf Of Aqaba ◽  
Fault Plane Solutions ◽  
Seismicity Parameters ◽  
Fault Parameters ◽  
The Moment ◽  
Seismic Deformation

Abstract The main goal of this study is to quantify the rate of seismic deformation in the Gulf of Aqaba. The moment tensor summation technique based on the seismicity data, for all available historical and instrumental data (1900-2019), and reliable fault plane solutions was used to calculate the size and the shape of deformation. For the period from 1900 to 2019, the seismicity data was used to calculate the seismicity parameters (representing by the Gutenberg-Richter and moment-magnitude relations) and the spatial extent of the deformation zone. The fault parameters of forty-four earthquakes, having moment magnitudes range from 3.2 to 7.2, were used to construct the moment tensor summation and subsequently to calculate the rate of seismic deformation. The calculations showed that a predominant shear deformation acting in the Gulf of Aqaba is taken up by extension in a direction of N40.8 o E at a rate of 0.83±0.21 mm/yr. and compression in a direction of N131.6 o E at a rate of 0.32±0.05 mm/yr.; reflecting the Gulf of Aqaba is undergoing from shear deformation accommodated along a strike-slip fault. The obtained results exhibited that the present-day deformation in the Gulf of Aqaba is acting by the interaction of relative tectonic motions among African, Sinai and Arabia plates.

scholarly journals Performance Evaluation of Different SAR-Based Techniques on the 2019 Ridgecrest Sequence

2021 ◽  
Vol 13 (4) ◽  
pp. 685
Author(s):  
Marco Polcari ◽  
Mimmo Palano ◽  
Marco Moro
Keyword(s):  
Performance Evaluation ◽  
Strike Slip ◽  
Seismic Sequence ◽  
Fault Rupture ◽  
Coseismic Displacement ◽  
Surface Rupture ◽  
Eastern California Shear Zone ◽  
Tectonic Framework ◽  
Gnss Network ◽  
The One

We evaluated the performances of different SAR-based techniques by analyzing the surface coseismic displacement related to the 2019 Ridgecrest seismic sequence (an Mw 6.4 foreshock on July 4th and an Mw 7.1 mainshock on July 6th) in the tectonic framework of the eastern California shear zone (Southern California, USA). To this end, we compared and validated the retrieved SAR-based coseismic displacement with the one estimated by a dense GNSS network, extensively covering the study area. All the SAR-based techniques constrained the surface fault rupture well; however, in comparison with the GNSS-based coseismic displacement, some significant differences were observed. InSAR data showed better performance than MAI and POT data by factors of about two and three, respectively, therefore confirming that InSAR is the most consolidated technique to map surface coseismic displacements. However, MAI and POT data made it possible to better constrain the azimuth displacement and to retrieve the surface rupture trace. Therefore, for cases of strike-slip earthquakes, all the techniques should be exploited to achieve a full synoptic view of the coseismic displacement field.

Microearthquake seismicity and tectonics of Coastal Northern California

1970 ◽  
Vol 60 (5) ◽  
pp. 1669-1699 ◽  
Author(s):  
Leonardo Seeber ◽  
Muawia Barazangi ◽  
Ali Nowroozi
Keyword(s):  
High Frequency ◽  
Fault Plane ◽  
San Andreas Fault ◽  
High Gain ◽  
Strike Slip ◽  
Fault System ◽  
Northern California ◽  
Fault Plane Solutions ◽  
Sharp Bend ◽  
San Andreas

Abstract This paper demonstrates that high-gain, high-frequency portable seismographs operated for short intervals can provide unique data on the details of the current tectonic activity in a very small area. Five high-frequency, high-gain seismographs were operated at 25 sites along the coast of northern California during the summer of 1968. Eighty per cent of 160 microearthquakes located in the Cape Mendocino area occurred at depths between 15 and 35 km in a well-defined, horizontal seismic layer. These depths are significantly greater than those reported for other areas along the San Andreas fault system in California. Many of the earthquakes of the Cape Mendocino area occurred in sequences that have approximately the same magnitude versus length of faulting characteristics as other California earthquakes. Consistent first-motion directions are recorded from microearthquakes located within suitably chosen subdivisions of the active area. Composite fault plane solutions indicate that right-lateral movement prevails on strike-slip faults that radiate from Cape Mendocino northwest toward the Gorda basin. This is evidence that the Gorda basin is undergoing internal deformation. Inland, east of Cape Mendocino, a significant component of thrust faulting prevails for all the composite fault plane solutions. Thrusting is predominant in the fault plane solution of the June 26 1968 earthquake located along the Gorda escarpement. In general, the pattern of slip is consistent with a north-south crustal shortening. The Gorda escarpment, the Mattole River Valley, and the 1906 fault break northwest of Shelter Cove define a sharp bend that forms a possible connection between the Mendocino escarpment and the San Andreas fault. The distribution of hypocenters, relative travel times of P waves, and focal mechanisms strongly indicate that the above three features are surface expressions of an important structural boundary. The sharp bend in this boundary, which is concave toward the southwest, would tend to lock the dextral slip along the San Andreas fault and thus cause the regional north-south compression observed at Cape Mendocino. The above conclusions support the hypothesis that dextral strike-slip motion along the San Andreas fault is currently being taken up by slip along the Mendocino escarpment as well as by slip along northwest trending faults in the Gorda basin.

The Chelmsford-Lowell, Massachusetts, earthquake of 23 November 1980: Depth control and fault plane solution

1981 ◽  
Vol 71 (4) ◽  
pp. 1369-1372
Author(s):  
Jay J. Pulli ◽  
Michael J. Guenette
Keyword(s):  
New England ◽  
Fault Plane ◽  
Seismic Station ◽  
Focal Depth ◽  
Strike Slip ◽  
Fault Plane Solution ◽  
Origin Time ◽  
Small Magnitude ◽  
Depth Control ◽  
Plane Solution

abstract On 23 November 1980, a small (magnitude 2.9) earthquake occurred on the Chelmsford-Lowell, Massachusetts, border, approximately 10 km northeast of the MIT seismic station at Westford, Massachusetts (WFM). Thus we were able to accurately determine the focal depth, which is generally not the case in New England. Our hypocentral solution was latitude 41.63, longitude −71.36, depth 1.5 km, at origin time 00:39:32.0 UTC. The fault plane solution shows either strike-slip or dip-slip faulting with a P axis trending NE-SW, which is in agreement with overcoring measurements in a nearby granite quarry.

Rampart seismic zone of central Alaska

1983 ◽  
Vol 73 (3) ◽  
pp. 813-829
Author(s):  
P. Yi-Fa Huang ◽  
N. N. Biswas
Keyword(s):  
Main Shock ◽  
Fault Plane ◽  
B Value ◽  
Aftershock Sequence ◽  
Strike Slip ◽  
Lithospheric Plate ◽  
Normal Faults ◽  
Seismic Zone ◽  
The West ◽  
Fault Plane Solutions

abstract This paper describes the characteristics of the Rampart seismic zone by means of the aftershock sequence of the Rampart earthquake (ML = 6.8) which occurred in central Alaska on 29 October 1968. The magnitudes of the aftershocks ranged from about 1.6 to 4.4 which yielded a b value of 0.96 ± 0.09. The locations of the aftershocks outline a NNE-SSW trending aftershock zone about 50 km long which coincides with the offset of the Kaltag fault from the Victoria Creek fault. The rupture zone dips steeply (≈80°) to the west and extends from the surface to a depth of about 10 km. Fault plane solutions for a group of selected aftershocks, which occurred over a period of 22 days after the main shock, show simultaneous occurrences of strike-slip and normal faults. A comparison of the trends in seismicity between the neighboring areas shows that the Rampart seismic zone lies outside the area of underthrusting of the lithospheric plate in southcentral and central Alaska. The seismic zone outlined by the aftershock sequence appears to represent the formation of an intraplate fracture caused by regional northwest compression.

Aftershock sequence and focal parameters of the February 28, 1969 earthquake of the Azores-Gibraltar fracture zone

1972 ◽  
Vol 62 (3) ◽  
pp. 699-719 ◽  
Author(s):  
A. López Arroyo ◽  
A. Udías
Keyword(s):  
Canary Islands ◽  
Fracture Zone ◽  
Main Shock ◽  
Fault Plane ◽  
Aftershock Sequence ◽  
Strike Slip ◽  
Strait Of Gibraltar ◽  
Wide Region ◽  
Focal Parameters ◽  
Source Mechanism Solution

Abstract The earthquake of February 28, 1969, which occurred about 500 km west of the Strait of Gibraltar, was felt over the entire Iberian Peninsula, in a wide region of Morocco, and south to the Canary Islands. It had a long sequence of aftershocks continuing for at least 10 months, but, nevertheless, most of the energy seems to have been liberated in the main shock of which the mb was 7.4. The source mechanism solution indicates a fault plane striking N 67°W and dipping 68°SW, with motion principally of the strike-slip type. There also is some overthrusting. The horizontal extent of faulting is of the order of 90 km.

scholarly journals Oblique convergence causes both thrust and strike-slip ruptures during the 2021 M 7.2 Haiti earthquake

2021 ◽  
Author(s):  
Ryo Okuwaki ◽  
Wenyuan Fan
Keyword(s):  
Strike Slip ◽  
Fault Rupture ◽  
Plate Convergence ◽  
Regional Deformation ◽  
Blind Thrust ◽  
Oblique Convergence ◽  
Block Movement ◽  
History Of ◽  
Tectonic Boundary ◽  
Blind Thrust Fault

A devastating magnitude 7.2 earthquake struck Southern Haiti on 14 August 2021. The earthquake caused severe damages and over 2000 casualties. Resolving the earthquake rupture process can provide critical insights into hazard mitigation. Here we use integrated seismological analyses to obtain the rupture history of the 2021 earthquake. We find the earthquake first broke a blind thrust fault and then jumped to a disconnected strike-slip fault. Neither of the fault configurations aligns with the left-lateral tectonic boundary between the Caribbean and North American plates. The complex multi-fault rupture may result from the oblique plate convergence in the region that the initial thrust rupture is due to the boundary-normal compression and the following strike-slip faulting originates from the Gonâve microplate block movement, orienting towards the SW-NE direction. The complex rupture development of the earthquake suggests that the regional deformation is accommodated by a network of segmented faults with diverse faulting conditions.

Aftershocks of the Benham nuclear explosion

1969 ◽  
Vol 59 (6) ◽  
pp. 2271-2281
Author(s):  
R. M. Hamilton ◽  
J. H. Healy
Keyword(s):  
Fault Plane ◽  
Nuclear Explosion ◽  
Test Site ◽  
Strike Slip ◽  
Nevada Test Site ◽  
Ground Zero ◽  
Fault Plane Solutions ◽  
Fault Movement ◽  
Near Surface ◽  
Earthquake Distribution

abstract The Benham nuclear explosion, a 1.1 megaton test 1.4 km beneath Pahute Mesa at the Nevada Test Site, initiated a sequence of earthquakes lasting several months. The epicenters of these shocks were located within 13 km of ground zero in several linear zones that parallel the regional fault trends. Focal depths range from near surface to 6 km. The earthquakes are not located in the zone of the major ground breakage. The earthquake distribution and fault plane solutions together indicate that both right-lateral strike-slip fault movement and dip-slip fault movement occurred. The explosion apparently caused the release of natural tectonic strain.

Sign in / Sign up

Export Citation Format

Share Document