Fault parameters of the Mw 6.4 January 7, 2020, Puerto Rico earthquake estimated from teleseismic, GNSS and InSAR data

2021 ◽  
Author(s):  
Adriano Nobile ◽  
Renier Viltres ◽  
Hannes Vasyura-Bathke ◽  
Daniele Trippanera ◽  
Wenbin Wenbin Xu ◽  
...  
Keyword(s):  
Puerto Rico ◽  
Fault Zone ◽  
Ground Deformation ◽  
Source Parameters ◽  
Active Faults ◽  
Geodetic Network ◽  
Seismic Sequence ◽  
Seismicity Rates ◽  
Fault Parameters ◽  
East West

<p>We used teleseismic waveforms and ground deformation data from GNSS and InSAR to estimate source fault parameters of the M<sub>w</sub>6.4 earthquake that occurred just offshore southwestern Puerto Rico on 7 January 2020. The mainshock was a part of an energetic seismic sequence that started on 28 December 2019 and led to a M<sub>w</sub>5.8 earthquake on 6 January 2020, a day before the M<sub>w</sub>6.4 mainshock. The ground-shaking due to the largest earthquakes of the sequence caused significant damage to buildings and infrastructures in Puerto Rico and one casualty was reported by the local media. The mainshock was followed by a strong aftershock sequence that included four M<sub>w </sub>≥ 5 events within the first 3 hours. In the first 40 days of the seismic sequence, data from the Puerto Rico Seismic Network were used to locate ~3800 earthquakes of magnitude > 2, illuminating an east-west elongated 30x50 km<sup>2</sup> area, just offshore the southwestern coast of Puerto Rico. The region affected by this activity was before characterized by relatively low seismicity rates, even if a system of active faults, both onshore and offshore, had been mapped. The sequence is peculiar due to its complex development and many large aftershocks (magnitude > 4.5), with the mainshock releasing only  ~60% of the total seismic moment.</p><p>We estimated the key source parameters of the mainshock using teleseismic data, GNSS data from the Puerto Rico Geodetic Network, and InSAR data from the Sentinel-1 and ALOS-2 satellites. The modeled source is consistent with a ~15 km long and ~11 km wide blind fault, oriented roughly east-west and dipping 46<sup>o</sup> towards north, and with up to 1.1 m of oblique normal and left-lateral strike-slip.</p><p>The optimal fault plane source indicates that it is an offshore continuation of the mapped North Boquerón Bay - Punta Montalva fault zone, supported by the large number of the aftershocks that trend along the same direction. However, most of the aftershocks, even those of magnitude > 5, occurred on other nearby faults, highlighting the complexity of this fault zone area.</p>

scholarly journals Application for source parameters calculations as input for static stress changes studies

2007 ◽  
Vol 40 (4) ◽  
pp. 2008
Author(s):  
P. M. Paradisopoulou ◽  
E. E. Papadimitriou ◽  
V. G. Karakostas ◽  
A. Kilias
Keyword(s):  
Scaling Laws ◽  
Source Parameters ◽  
Active Faults ◽  
Static Stress ◽  
Coulomb Stress ◽  
Coseismic Slip ◽  
Earthquake Source Parameters ◽  
Fault Parameters ◽  
Stress Changes ◽  
Stress Application

The study of static Coulomb Stress changes requires initially the collection of information on the major active faults in a study area concerning their geometry and kinematic properties and then a series of complex calculation for stress changes that are associated with both coseismic displacements of the stronger events and the tectonic loading on these major faults. The Coulomb Stress Application has been developed as a tool to provide a user-friendly way of entering the necessary data and an efficient way to perform the complex calculations procedure. More specifically the aim of the application is a) the collection of data (catalogues of earthquakes, fault parameters) in a relational database, b) the calculation of earthquake source parameters such as the length and the width of the causative fault, and the coseismic slip by using available scaling laws, and finally, c) the execution of all the necessary programs and scripts (e.g. dis3dop.exe, GMT package) to get a map of static stress changes for an area. Coulomb Stress application provides a way to store these data for a study area and it is a method to perform a series of calculations by plotting a series of maps and examine the results for a number of cases.

Transtensional Rupture within a Diffuse Plate Boundary Zone during the 2020 Mw 6.4 Puerto Rico Earthquake

2021 ◽  
Author(s):  
Renier Viltres ◽  
Adriano Nobile ◽  
Hannes Vasyura-Bathke ◽  
Daniele Trippanera ◽  
Wenbin Xu ◽  
...  
Keyword(s):  
Puerto Rico ◽  
Plate Boundary ◽  
Large Earthquake ◽  
Satellite System ◽  
Coseismic Deformation ◽  
Fault Parameters ◽  
Earthquake Potential ◽  
Global Navigation Satellite ◽  
Plate Boundary Zone ◽  
East West

Abstract On 7 January 2020, an Mw 6.4 earthquake occurred in the northeastern Caribbean, a few kilometers offshore of the island of Puerto Rico. It was the mainshock of a complex seismic sequence, characterized by a large number of energetic earthquakes illuminating an east–west elongated area along the southwestern coast of Puerto Rico. Deformation fields constrained by Interferometric Synthetic Aperture Radar and Global Navigation Satellite System data indicate that the coseismic movements affected only the western part of the island. To assess the mainshock’s source fault parameters, we combined the geodetically derived coseismic deformation with teleseismic waveforms using Bayesian inference. The results indicate a roughly east–west oriented fault, dipping northward and accommodating ∼1.4 m of transtensional motion. Besides, the determined location and orientation parameters suggest an offshore continuation of the recently mapped North Boquerón Bay–Punta Montalva fault in southwest Puerto Rico. This highlights the existence of unmapped faults with moderate-to-large earthquake potential within the Puerto Rico region.

Response and initial scientific findings from the southwestern Puerto Rico 2020 Seismic Sequence

Temblor ◽  
2020 ◽  
Author(s):  
Alberto López ◽  
K. Stephen Hughes ◽  
Thomas Hudgins ◽  
Elizabeth Vanacore ◽  
Gisela Báez-Sánchez
Keyword(s):  
Puerto Rico ◽  
Seismic Sequence

Failure Analysis Of Buried Gas Pipelines Crossing Seismic Faults

2020 ◽  
Vol 3 (2) ◽  
pp. 781-790
Author(s):  
M. Rizwan Akram ◽  
Ali Yesilyurt ◽  
A.Can. Zulfikar ◽  
F. Göktepe
Keyword(s):  
Ground Deformation ◽  
Warning System ◽  
Strike Slip ◽  
Gas Pipelines ◽  
Steel Pipes ◽  
Seismic Fault ◽  
Fault Parameters ◽  
Dip Angle ◽  
Permanent Ground Deformation ◽  
Recent Earthquakes

Research on buried gas pipelines (BGPs) has taken an important consideration due to their failures in recent earthquakes. In permanent ground deformation (PGD) hazards, seismic faults are considered as one of the major causes of BGPs failure due to accumulation of impermissible tensile strains. In current research, four steel pipes such as X-42, X-52, X-60, and X-70 grades crossing through strike-slip, normal and reverse seismic faults have been investigated. Firstly, failure of BGPs due to change in soil-pipe parameters have been analyzed. Later, effects of seismic fault parameters such as change in dip angle and angle between pipe and fault plane are evaluated. Additionally, effects due to changing pipe class levels are also examined. The results of current study reveal that BGPs can resist until earthquake moment magnitude of 7.0 but fails above this limit under the assumed geotechnical properties of current study. In addition, strike-slip fault can trigger early damage in BGPs than normal and reverse faults. In the last stage, an early warning system is proposed based on the current procedure. 

Source Parameters for 1999 North Anatolian Fault Zone Aftershocks

2009 ◽  
Vol 166 (4) ◽  
pp. 547-566 ◽  
Author(s):  
Rengin Gök ◽  
Lawrence Hutchings ◽  
Kevin Mayeda ◽  
Doğan Kalafat
Keyword(s):  
Fault Zone ◽  
Source Parameters ◽  
North Anatolian Fault ◽  
North Anatolian Fault Zone

The 2019 Ms 4.2 and 5.2 Beiliu Earthquake Sequence in South China: Complex Conjugate Strike-Slip Faulting Revealed by Rupture Directivity Analysis

2021 ◽  
Author(s):  
Xiaohui He ◽  
Hao Liang ◽  
Peizhen Zhang ◽  
Yue Wang
Keyword(s):  
South China ◽  
Source Parameters ◽  
Active Faults ◽  
Fault Zones ◽  
Strike Slip ◽  
P Wave ◽  
Complex Conjugate ◽  
South China Block ◽  
Rupture Directivity ◽  
Time Duration

Abstract The South China block has been one of the most seismically quiescent regions in China, and the geometries and activities of the Quaternary faults have remained less studied due to the limited outcrops. Thus, source parameters of small-to-moderate earthquakes are important to help reveal the location, geometry distribution, and mechanical properties of the subsurface faults and thus improve the seismic risk assessment. On 12 October 2019, two earthquakes (the Ms 4.2 foreshock and the Ms 5.2 mainshock) occurred within 2 s and are located in southern South China block, near the junction region of the large-scale northeast-trending fault zones and the less continuous northwest-trending fault zones. We determined the point-source parameters of the two events via P-wave polarity analysis and regional waveform modeling, and the resolved focal mechanisms are significantly different with the minimum 3D rotation angle of 52°. We then resolved the rupture directivity of the two events by analyzing the azimuth variation of the source time duration and found the Ms 4.2 foreshock ruptured toward north-northwest for ∼1.0 km, and the Ms 5.2 mainshock ruptured toward east-southeast (ESE) for ∼1.5 km, implying conjugate strike-slip faulting. The conjugate causative faults have not been mapped on the regional geological map, and we infer that the two faults may be associated with the northwest-trending Bama-Bobai fault zone (the Shiwo section). These active faults are optimally oriented in the present-day stress field (northwest-southeast) and thus may now be potentially accumulating elastic strain to be released in a future large earthquake.

Seismic doublets and a complex seismic sequence controlled by the rotation of the Juan Fernández microplate

2021 ◽  
Author(s):  
Simone Cesca ◽  
Carla Valenzuela Malebrán ◽  
José Ángel López-Comino ◽  
Timothy Davis ◽  
Carlos Tassara ◽  
...  
Keyword(s):  
Source Parameters ◽  
Strike Slip ◽  
Focal Mechanisms ◽  
Joint Analysis ◽  
Seismic Sequence ◽  
Local Data ◽  
Study Region ◽  
Coulomb Stress Changes ◽  
Earthquake Source Parameters ◽  
Stress Changes

<p> A complex seismic sequence took place in 2014 at the Juan Fernández microplate, a small microplate located between Pacific, Nazca and Antarctica plates. Despite the remoteness of the study region and the lack of local data, we were able to resolve earthquake source parameters and to reconstruct the complex seismic sequence, by using modern waveform-based seismological techniques. The sequence started with an exceptional Mw 7.1-6.7 thrust – strike slip earthquake doublet, the first subevent being the largest earthquake ever recorded in the region and one of the few rare thrust earthquakes in a region otherwise characterized by normal faulting and strike slip earthquakes. The joint analysis of seismicity and focal mechanisms suggest the activation of E-W and NE-SW faults or of an internal curved pseudofault, which is formed in response to the microplate rotation, with alternation of thrust and strike-slip earthquakes. Seismicity migrated Northward in its final phase, towards the microplate edge, where a second doublet with uneven focal mechanisms occurred. The sequence rupture kinematics is well explained by Coulomb stress changes imparted by the first subevent. Our analysis show that compressional stresses, which have been mapped at the northern boundary of the microplate, but never accompanied by large thrust earthquakes, can be accommodated by the rare occurrence of large, impulsive, shallow thrust earthquakes, with a considerable tsunamigenic potential.</p>

Do active faults’ clay mineral compositions affect whether earthquake ruptures they host will displace the surface?

2021 ◽  
Author(s):  
Selina S. Fenske ◽  
Virginia G. Toy ◽  
Bernhard Schuck ◽  
Anja M. Schleicher ◽  
Klaus Reicherter
Keyword(s):  
Fault Zone ◽  
Clay Mineral ◽  
Active Faults ◽  
Surface Displacement ◽  
Surface Rupture ◽  
Near Surface ◽  
Ground Shaking ◽  
Physical Measurements ◽  
Surface Displacements ◽  
Earthquake Ruptures

<p>The tectonophysical paradigm that earthquake ruptures should not start, or easily propagate into, the shallowest few kilometers of Earth’s crust makes it difficult to understand why damaging surface displacements have occurred during historic events. The paradigm is supported by decades of analyses demonstrating that near the surface, most major fault zones are composed of clay minerals – particularly extraordinarily weak smectites – which most laboratory physical measurements suggest should prevent surface rupture if present. Recent studies of New Zealand’s Alpine Fault Zone (AFZ) demonstrate smectites are absent from some near surface fault outcrops, which may explain why this fault was able to offset the surface locally in past events. The absence of smectites in places within the AFZ can be attributed to locally exceptionally high geothermal gradients related to circulation of meteoric (surface-derived) water into the fault zone, driven by significant topographic gradients. The record of surface rupture of the AFZ is heterogeneous, and no one has yet systematically examined the distribution of segments devoid of evidence for recent displacement. There are significant implications for seismic hazard, which comprises both surface displacements and ground shaking with intensity related to the area of fault plane that ruptures (which will be reduced if ruptures do not reach the surface).  We will present results of new rigorous XRD clay mineral analyses of AFZ principal slip zone gouges that indicate where smectites are present, and consider if these display systematic relationships to surface displacement records. We also plan to apply the same methodology to the Carboneras Fault Zone in Spain, and the infrequent Holocene-active faults in Western Germany.</p>

Mature diffuse tectonic block boundary revealed by the 2020 southwestern Puerto Rico seismic sequence

2021 ◽  
Author(s):  
Uri S ten Brink ◽  
Elizabeth Vanacore ◽  
Eric J. Fielding ◽  
Jason D Chaytor ◽  
Alberto M Lopez-Venegas ◽  
...  
Keyword(s):  
Puerto Rico ◽  
Tectonic Block ◽  
Seismic Sequence ◽  
Block Boundary
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