25-Second Determination of 2019 Mw 7.1 Ridgecrest Earthquake Coseismic Deformation

2020 ◽  
Vol 110 (4) ◽  
pp. 1680-1687 ◽  
Author(s):  
Timothy I. Melbourne ◽  
Walter M. Szeliga ◽  
V. Marcelo Santillan ◽  
Craig W. Scrivner
Keyword(s):  
Mojave Desert ◽  
Seismic Waves ◽  
Ground Deformation ◽  
Cumulative Effect ◽  
Satellite System ◽  
Coseismic Deformation ◽  
Fault Rupture ◽  
Fault Creep ◽  
Origin Time ◽  
Rupture Duration

ABSTRACT We have developed a global earthquake monitoring system based on low-latency measurements from more than 1000 existing Global Navigational Satellite System (GNSS) receivers, of which nine captured the 2019 Mw 6.4 Ridgecrest, California, foreshock and Mw 7.1 mainshock earthquakes. For the foreshock, coseismic offsets of up to 10 cm are resolvable on one station closest to the fault, but did not trigger automatic offset detection. For the mainshock, GNSS monitoring determined its coseismic deformation of up to 70 cm on nine nearby stations within 25 s of event nucleation. These 25 s comprise the fault rupture duration itself (roughly 10 s of peak moment release), another 10 s for seismic waves and displacement to propagate to nearby GNSS stations, and a few additional seconds for surface waves and other crustal reverberations to dissipate sufficiently such that coseismic offset estimation filters could reconverge. Latency between data acquisition in the Mojave Desert and positioning in Washington State averaged 1.4 s, a small fraction of the fault rupture time itself. GNSS position waveforms for the two closest stations that show the largest dynamic and static displacements agree well with postprocessed time series. Mainshock coseismic ground deformation estimated within 25 s of origin time also agrees well with, but is ∼10% smaller than, deformation estimated using 48 hr observation windows, which may reflect rapid postseismic fault creep or the cumulative effect of nearly 1000 aftershocks in the 48 hr following the mainshock. GNSS position waveform shapes, which comprise a superposition of dynamic and static displacements, are well modeled by frequency–wavenumber synthetics for the Hadley–Kanamori 1D crustal structure model and the U.S. Geological Survey finite-rupture distribution and timing. These results show that GNSS seismic monitoring performed as designed and offers a new means of rapidly characterizing large earthquakes globally.

scholarly journals Instrumental study of the Manix Earthquakes*

1951 ◽  
Vol 41 (4) ◽  
pp. 347-388
Author(s):  
C. F. Richter ◽  
J. M. Nordquist
Keyword(s):  
Mojave Desert ◽  
Seismic Waves ◽  
Large Angle ◽  
Strike Slip ◽  
The Other ◽  
Origin Time ◽  
Left Hand ◽  
Instrumental Study ◽  
Group A ◽  
The Times

Summary Readings from seismograms of thirty-eight shocks occurring on the Mojave Desert near Manix, California, are tabulated, plotted, and discussed. For a large proportion of the shocks (Groups A and D), the most clearly identified seismic waves have travel times as follows (times in seconds, Δ in kilometers): p–O=D/6.34P–O=–1.2 + 0.1799 ΔPn–O=5.4 + 0.12195 Δs–O=D/3.67Pm–O=3.9 + 0.1427 ΔSn–O=9.0 + 0.220 ΔPy–O=1.2 + 0.1610 ΔSa–O=6.0 + 0.25 Δ D is calculated from Δ assuming a depth of 16 km. For the remaining shocks (Groups B and C), the constant terms in the equations for Pn, Pm, Py are increased to 6.0, 4.5, and 2.2, respectively; the other equations are unchanged, but D is calculated for a depth of 10 km. The Group A shocks are assigned to four subgroups. Epicenters are as follows: GroupLat. NLong. WA1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34°57.5116°32′A2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3459.511633.5A3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .345811633A4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .350011634B. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .345611631C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3457.511632D. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .345311637 Epicenters A1 to B follow an alignment striking about N 30° W, crossing the Manix fault at a large angle. No shocks are located elsewhere along the Manix fault, but the smaller shocks cannot be placed accurately. The principal earthquake, of magnitude 6.2, is assigned to the A2 epicenter, with origin time 07:58:05.6 P.S.T. (15:58:05.6 G.C.T.), April 10, 1947. This agrees well with the times recorded at distant stations. A catalogue is given listing all subsequent shocks of magnitude 3.0 or greater in the area to the end of April, 1950, with assignment to one of the groups when possible. Recorded initial compressions and dilatations at the several stations are equally consistent with right-hand strike-slip on a hypothetical fault following the line of located epicenters, or with left-hand strike-slip on the Manix fault; the latter displacement was actually found. It is suggested that both occurred. Representative seismograms are reproduced.

scholarly journals Copernicus Sentinel-1 MT-InSAR, GNSS and Seismic Monitoring of Deformation Patterns and Trends at the Methana Volcano, Greece

2020 ◽  
Vol 10 (18) ◽  
pp. 6445 ◽  
Author(s):  
Theodoros Gatsios ◽  
Francesca Cigna ◽  
Deodato Tapete ◽  
Vassilis Sakkas ◽  
Kyriaki Pavlou ◽  
...  
Keyword(s):  
Land Surface ◽  
Surface Deformation ◽  
Ground Deformation ◽  
Local Population ◽  
Seasonal Fluctuation ◽  
Satellite System ◽  
Deformation Monitoring ◽  
Persistent Scatterers ◽  
Geothermal Activity ◽  
Global Navigation Satellite

The Methana volcano in Greece belongs to the western part of the Hellenic Volcanic Arc, where the African and Eurasian tectonic plates converge at a rate of approximately 3 cm/year. While volcanic hazard in Methana is considered low, the neotectonic basin constituting the Saronic Gulf area is seismically active and there is evidence of local geothermal activity. Monitoring is therefore crucial to characterize any activity at the volcano that could impact the local population. This study aims to detect surface deformation in the whole Methana peninsula based on a long stack of 99 Sentinel-1 C-band Synthetic Aperture Radar (SAR) images in interferometric wide swath mode acquired in March 2015–August 2019. A Multi-Temporal Interferometric SAR (MT-InSAR) processing approach is exploited using the Interferometric Point Target Analysis (IPTA) method, involving the extraction of a network of targets including both Persistent Scatterers (PS) and Distributed Scatterers (DS) to augment the monitoring capability across the varied land cover of the peninsula. Satellite geodetic data from 2006–2019 Global Positioning System (GPS) benchmark surveying are used to calibrate and validate the MT-InSAR results. Deformation monitoring records from permanent Global Navigation Satellite System (GNSS) stations, two of which were installed within the peninsula in 2004 (METH) and 2019 (MTNA), are also exploited for interpretation of the regional deformation scenario. Geological, topographic, and 2006–2019 seismological data enable better understanding of the ground deformation observed. Line-of-sight displacement velocities of the over 4700 PS and 6200 DS within the peninsula are from −18.1 to +7.5 mm/year. The MT-InSAR data suggest a complex displacement pattern across the volcano edifice, including local-scale land surface processes. In Methana town, ground stability is found on volcanoclasts and limestone for the majority of the urban area footprint while some deformation is observed in the suburban zones. At the Mavri Petra andesitic dome, time series of the exceptionally dense PS/DS network across blocks of agglomerate and cinder reveal seasonal fluctuation (5 mm amplitude) overlapping the long-term stable trend. Given the steepness of the slopes along the eastern flank of the volcano, displacement patterns may indicate mass movements. The GNSS, seismological and MT-InSAR analyses lead to a first account of deformation processes and their temporal evolution over the last years for Methana, thus providing initial information to feed into the volcano baseline hazard assessment and monitoring system.

scholarly journals From fault creep to slow and fast earthquakes in carbonates

Geology ◽  
2019 ◽  
Vol 47 (8) ◽  
pp. 744-748 ◽  
Author(s):  
Franҫois X. Passelègue ◽  
Jérôme Aubry ◽  
Aurélien Nicolas ◽  
Michele Fondriest ◽  
Damien Deldicque ◽  
...  
Keyword(s):  
Seismic Waves ◽  
Central Italy ◽  
Confining Pressure ◽  
Mediterranean Area ◽  
Rupture Propagation ◽  
Fault Creep ◽  
Seismogenic Layer ◽  
Elastic Loading ◽  
High Frequency Seismic Waves ◽  
Hypocentral Location

Abstract A major part of the seismicity striking the Mediterranean area and other regions worldwide is hosted in carbonate rocks. Recent examples are the destructive earthquakes of L’Aquila (Mw 6.1) in 2009 and Norcia (Mw 6.5) in 2016 in central Italy. Surprisingly, within this region, fast (≈3 km/s) and destructive seismic ruptures coexist with slow (≤10 m/s) and nondestructive rupture phenomena. Despite its relevance for seismic hazard studies, the transition from fault creep to slow and fast seismic rupture propagation is still poorly constrained by seismological and laboratory observations. Here, we reproduced in the laboratory the complete spectrum of natural faulting on samples of dolostones representative of the seismogenic layer in the region. The transitions from fault creep to slow ruptures and from slow to fast ruptures were obtained by increasing both confining pressure (P) and temperature (T) up to conditions encountered at 3–5 km depth (i.e., P = 100 MPa and T = 100 °C), which corresponds to the hypocentral location of slow earthquake swarms and the onset of seismicity in central Italy. The transition from slow to fast rupture is explained by an increase in the ambient temperature, which enhances the elastic loading stiffness of the fault, i.e., the slip velocities during nucleation, allowing flash weakening and, in turn, the propagation of fast ruptures radiating intense high-frequency seismic waves.

scholarly journals Geodetic Study of the 2006–2010 Ground Deformation in La Palma (Canary Islands): Observational Results

2020 ◽  
Vol 12 (16) ◽  
pp. 2566
Author(s):  
Joaquín Escayo ◽  
José Fernández ◽  
Juan F. Prieto ◽  
Antonio G. Camacho ◽  
Mimmo Palano ◽  
...  
Keyword(s):  
Canary Islands ◽  
Surface Deformation ◽  
Ground Deformation ◽  
Satellite System ◽  
Point Of View ◽  
Synthetic Aperture Radar Interferometry ◽  
La Palma ◽  
Moderate Seismicity ◽  
Definition Of ◽  
Global Navigation Satellite

La Palma is one of the youngest of the Canary Islands, and historically the most active. The recent activity and unrest in the archipelago, the moderate seismicity observed in 2017 and 2018 and the possibility of catastrophic landslides related to the Cumbre Vieja volcano have made it strongly advisable to ensure a realistic knowledge of the background surface deformation on the island. This will then allow any anomalous deformation related to potential volcanic unrest on the island to be detected by monitoring the surface deformation. We describe here the observation results obtained during the 2006–2010 period using geodetic techniques such as Global Navigation Satellite System (GNSS), Advanced Differential Synthetic Aperture Radar Interferometry (A-DInSAR) and microgravimetry. These results show that, although there are no significant associated variations in gravity, there is a clear surface deformation that is spatially and temporally variable. Our results are discussed from the point of view of the unrest and its implications for the definition of an operational geodetic monitoring system for the island.

Ground deformation associated with the August 2019 eruption of Piton de la Fournaise (La Réunion Island) inferred from DInSAR measurements

2020 ◽  
Author(s):  
Vincenzo De Novellis ◽  
Francesco Casu ◽  
Claudio De Luca ◽  
Mariarosaria Manzo ◽  
Fernando Monterroso ◽  
...  
Keyword(s):  
Ground Deformation ◽  
Coseismic Deformation ◽  
Southeastern Part ◽  
Eruptive Fissure ◽  
Piton De La Fournaise ◽  
Synthetic Aperture Radar Interferometry ◽  
Small Baseline Subset ◽  
Small Baseline ◽  
Deformation Patterns ◽  
Eruptive Fissures

<p>Piton de la Fournaise volcano forms the southeastern part of La Réunion, an oceanic basaltic island in the southernmost part of Mascarene Basin (Indian Ocean). Five eruptions occurred at Piton in 2019, accompanied by seismic activity, lava flow, and lava fountaining. Here below, we focus on the fourth eruption occurred between August 11 and 15 on the southern-southeastern flank of the volcano, inside the Enclos Fouqué caldera. This eruption was characterized by the opening of two eruptive fissures. We retrieve the surface deformations induced by the eruptive activity through space-borne Differential Synthetic Aperture Radar Interferometry (DInSAR) measurements. First, we generated the coseismic deformation maps by applying the DInSAR technique to SAR data collected along ascending and descending orbits by the Sentinel-1 constellation of the European Copernicus Programme. The DInSAR technique allows us to analyze the deformation patterns caused by the 11 August 2019 eruption. We also retrieved the pre-eruptive deformation through the Small BAseline Subset (SBAS) DInSAR approach. Then, we modelled the DInSAR displacements to constrain the geometry and characteristics of the eruptive source. The modelling results suggest that the observed deformation can be attributed to the interaction between a shallow magma reservoir located at ~1.5-2 km depth below the summit, and the intrusion of a dike feeding the eruptive fissure inside the Enclos Fouqué caldera.</p><p><em>This work is supported by: the 2019-2021 IREA-CNR and Italian Civil Protection Department agreement; the EPOS-SP project (GA 871121); and the I-AMICA (PONa3_00363) project.</em></p>

scholarly journals Precise Locating of the Great 1897 Shillong Plateau Earthquake Using Teleseismic and Regional Seismic Phase Data

2021 ◽  
Vol 1 (3) ◽  
pp. 135-144
Author(s):  
Shiba Subedi ◽  
György Hetényi
Keyword(s):  
Seismic Waves ◽  
Active Faults ◽  
Eastern Himalaya ◽  
Great Earthquake ◽  
Shillong Plateau ◽  
Time Data ◽  
Origin Time ◽  
Velocity Models ◽  
Rupture Plane ◽  
Phase Data

Abstract Pinched between the Eastern Himalaya and the Indo-Burman ranges, the Shillong Plateau represents a zone of distributed deformation with numerous visible and buried active faults. In 1897, a great (magnitude 8+) earthquake occurred in the area, and although a subsurface rupture plane has been proposed geodetically, its epicenter remained uncertain. We gathered original arrival time data of seismic waves from this early-instrumental era and combined them with modern, 3D velocity models to constrain the origin time and epicenter of this event, including uncertainties. Our results show that the earthquake has taken place in the northwest part of the plateau, at the junction of the short, surface-rupturing Chedrang fault and the buried Oldham fault (26.0°N, 90.7°E). This latter fault has been proposed earlier based on geodetic data and is long enough to host a great earthquake. Rupture has most likely propagated eastward. Stress change from the 1897 earthquake may have ultimately triggered the 1930 M 7.1 Dhubri earthquake, along a fault connecting the Shillong Plateau with the Himalaya.

scholarly journals The 2018–2019 seismo-volcanic crisis east of Mayotte, Comoros islands: seismicity and ground deformation markers of an exceptional submarine eruption

2020 ◽  
Vol 223 (1) ◽  
pp. 22-44 ◽  
Author(s):  
Anne Lemoine ◽  
Pierre Briole ◽  
Didier Bertil ◽  
Agathe Roullé ◽  
Michael Foumelis ◽  
...  
Keyword(s):  
Ground Deformation ◽  
Low Frequency ◽  
Harmonic Oscillation ◽  
Satellite System ◽  
First Year ◽  
Secondary Source ◽  
Magma Intrusion ◽  
Volcanic Event ◽  
Volcanic Islands ◽  
Global Navigation Satellite

SUMMARY On 10 May 2018, an unprecedented long and intense seismic crisis started offshore, east of Mayotte, the easternmost of the Comoros volcanic islands. The population felt hundreds of events. Over the course of 1 yr, 32 earthquakes with magnitude greater than 5 occurred, including the largest event ever recorded in the Comoros (Mw = 5.9 on 15 May 2018). Earthquakes are clustered in space and time. Unusual intense long lasting monochromatic very long period events were also registered. From early July 2018, Global Navigation Satellite System (GNSS) stations and Interferometric Synthetic Aperture Radar (InSAR) registered a large drift, testimony of a large offshore deflation. We describe the onset and the evolution of a large magmatic event thanks to the analysis of the seismicity from the initiation of the crisis through its first year, compared to the ground deformation observation (GNSS and InSAR) and modelling. We discriminate and characterize the initial fracturing phase, the phase of magma intrusion and dyke propagation from depth to the subsurface, and the eruptive phase that starts on 3 July 2018, around 50 d after the first seismic events. The eruption is not terminated 2 yr after its initiation, with the persistence of an unusual seismicity, whose pattern has been similar since summer 2018, including episodic very low frequency events presenting a harmonic oscillation with a period of ∼16 s. From July 2018, the whole Mayotte Island drifted eastward and downward at a slightly increasing rate until reaching a peak in late 2018. At the apex, the mean deformation rate was 224 mm yr−1 eastward and 186 mm yr−1 downward. During 2019, the deformation smoothly decreased and in January 2020, it was less than 20 per cent of its peak value. A deflation model of a magma reservoir buried in a homogenous half space fits well the data. The modelled reservoir is located 45 ± 5 km east of Mayotte, at a depth of 28 ± 3 km and the inferred magma extraction at the apex was ∼94 m3 s−1. The introduction of a small secondary source located beneath Mayotte Island at the same depth as the main one improves the fit by 20 per cent. While the rate of the main source drops by a factor of 5 during 2019, the rate of the secondary source remains stable. This might be a clue of the occurrence of relaxation at depth that may continue for some time after the end of the eruption. According to our model, the total volume extracted from the deep reservoir was ∼2.65 km3 in January 2020. This is the largest offshore volcanic event ever quantitatively documented. This seismo-volcanic crisis is consistent with the trans-tensional regime along Comoros archipelago.

Earthquakes and faults

1963 ◽  
Vol 53 (5) ◽  
pp. 873-891 ◽  
Author(s):  
F. F. Evison
Keyword(s):  
Seismic Waves ◽  
Surface Phenomenon ◽  
Local Phase ◽  
Fault Creep ◽  
Satisfactory Explanation ◽  
Underground Nuclear Explosions ◽  
Nuclear Explosions ◽  
Shallow Earthquakes ◽  
Deep Focus ◽  
Natural Earthquakes

Abstract The hypothesis that earthquakes are caused by faulting has been prominent in seismological theory for half a century, but continues to present many difficulties. Although the chief support comes from studies of large shallow earthquakes that have been accompanied by surface faulting, the evidence given by these infrequent events can be interpreted otherwise. No satisfactory explanation of deep-focus earthquakes has emerged; sudden faulting may be essentially a surface phenomenon. Nor does the hypothesis aid the understanding of such phenomena as sudden regional uplift, or slow fault creep. There is much to encourage the view that fracture of the ground is but a gross form of earthquake damage. On the other hand, the similarity between natural earthquakes and underground nuclear explosions, as radiators of seismic waves, suggests that sudden local phase transitions may provide a source mechanism for earthquakes at all depths.

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.

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