Template matching applied to the seismicity of the Albstadt Shear Zone, SW Germany

2021 ◽  
Author(s):  
Sarah Mader ◽  
Andrea Brüstle ◽  
Joachim R. R. Ritter ◽  
Keyword(s):  
Shear Zone ◽  
Template Matching ◽  
Strong Motion ◽  
Active Regions ◽  
High Gain ◽  
Seismic Network ◽  
Seismogenic Zone ◽  
Earthquake Catalog ◽  
Active Structures ◽  
The Town

<p>The Swabian Alb near the town of Albstadt, SW Germany, is one of the seismically most active regions in Central Europe. Since the beginning of the twentieth century continuous seismic activity is observed. At least three earthquakes with magnitudes greater than 5 occurred, causing major damages on the buildings in the closer vicinity. Despite of the size of these earthquakes no rupture structures are visible on the Earth’s surface. Earthquake locations are concentrated along a N-S striking zone, the so-called Albstadt Shear Zone (ASZ), at focal depths of about 1 km to 18 km. The central part of this seismogenic zone has an extension of approximately 20 km to 30 km and is characterized by dominantly sinistral strike-slip focal mechanisms. <br><br>The State Earthquake Service of Baden-Württemberg (LED) operates a dense seismic network of 6 high-gain and 9 strong-motion stations in the area of the ASZ. In 2015 and in 2018, 9 temporary high-gain stations were deployed nearby the center structure of ASZ within the framework of AlpArray Project and StressTransfer Network. This densified seismic network gives a unique opportunity to detect and locate the seismically active structures of the ASZ in more detail.</p><p>Therefore, a template matching algorithm is applied for microseismic earthquake detections. Results are compared with the existing earthquake catalog of the LED and statistics of the outcome are presented.</p>

The nature of the Albstadt Shear Zone, Germany

2020 ◽  
Author(s):  
Sarah Mader ◽  
Klaus Reicherter ◽  
Joachim Ritter ◽  
the AlpArray Working Group
Keyword(s):  
Shear Zone ◽  
Seismic Velocity ◽  
Active Regions ◽  
Velocity Model ◽  
Strike Slip ◽  
Fault System ◽  
Earthquake Catalog ◽  
Depth Range ◽  
Study Region ◽  
The Town

<p><span>The region around the town of Albstadt, SW Germany, is one of the most seismically active regions in Central Europe. In the last century alone three earthquakes with a magnitude greater than five happened and caused major damage. The ruptures occur along the Albstadt Shear Zone (ASZ), an approx. 20-30 km long, N-S striking fault with left-lateral strike slip. As there is no evidence for surface rupture the nature of the Albstadt Shear Zone can only be studied by its seismicity.</span></p><p><span>To characterize the ASZ we </span><span>continuously</span><span> complement the earthquake catalog of the </span><span>State Earthquake Service</span><span> of Baden-Württemberg with additional seismic phase onsets. For the latter we use the station network of AlpArray as well as </span><span>5 </span><span>additional, </span><span>in 2018/2019</span><span> installed seismic stations from the KArlsruhe BroadBand Array. </span><span>W</span><span>e invert</span><span>ed</span><span> for </span><span>a </span><span>new minimum 1D </span><span>seismic </span><span>velocity model</span> <span>of the study region. </span><span>We use this seismic velocity model to relocalize the complemented catalog</span> <span>and to calculate focal mechanisms</span><span>. </span></p><p><span>The majority of the seismicity happens between the towns Tübingen and Albstadt at around 9°E in a depth range of </span><span>about 1.5 to 16 km </span><span>and aligns </span><span>n</span><span>orth-</span><span>s</span><span>outh</span><span>. </span><span>Additionally, we see </span><span>a </span><span>cluster</span><span>ing of events at the town</span><span>s</span><span> Hechingen and Albstadt.</span><span> The dominating focal mechanism is strike-slip, </span><span>but we also observe </span><span>minor components of </span><span>normal and reverse faulting.<br></span><span>Our results image the ASZ by its mainly micro-seismic activity b</span><span>etween</span><span> 2011 </span><span>and</span><span> 2018 </span><span>confirming the N-S striking character, but also indicating a more complex fault system.</span></p><p><span>We thank the </span><span>State Earthquake Service</span><span> in Freiburg for using their data (Az. 4784//18_3303). </span></p><p> </p>

5 May 2014 MW 6.1 Mae Lao (Northern Thailand) Earthquake: Interpretations of Recorded Ground Motion and Structural Damage

2016 ◽  
Vol 32 (2) ◽  
pp. 1209-1238 ◽  
Author(s):  
Teraphan Ornthammarath ◽  
Pennung Warnitchai
Keyword(s):  
Structural Damage ◽  
Shear Failure ◽  
Main Shock ◽  
Ground Motions ◽  
Strong Motion ◽  
Earthquake Catalog ◽  
Northern Thailand ◽  
Epicentral Area ◽  
Soft Story ◽  
The Town

A moderate left-lateral strike-slip earthquake of MW 6.1 occurred on 5 May 2014 in northern Thailand, causing damage to the town of Mae Lao and nearby municipalities. Based on an instrumental earthquake catalog, the Mae Lao earthquake is the second largest earthquake in modern Thai history after the MW 6.3 Nan earthquake in 1935. In this study, the strong-motion records from the epicentral area are analyzed in order to investigate the characteristics of the ground motions. In addition, post-earthquake field observations and statistics for typical structural damage in the affected area, such as the soft story effect and the shear failure of columns, are summarized. Besides major structural damage, the majority of structures in the epicentral area withstood the strong motion, which could be due to the low stress drop of the main shock (40 bars) leading to below average ground motions for an MW 6.1 earthquake.

Evolution of the Kandilli Observatory and Earthquake Research Institute (KOERI) Seismic Network and the Data Center Facilities as a Primary Node of EIDA

2021 ◽  
Author(s):  
Musavver Didem Cambaz ◽  
Mehmet Özer ◽  
Yavuz Güneş ◽  
Tuğçe Ergün ◽  
Zafer Öğütcü ◽  
...  
Keyword(s):  
Data Center ◽  
Strong Motion ◽  
Seismic Network ◽  
Data Archive ◽  
Seismic Stations ◽  
Earthquake Research ◽  
Earthquake Research Institute ◽  
Research Facilities ◽  
Research Institute

Abstract As the earliest institute in Turkey dedicated to locating, recording, and archiving earthquakes in the region, the Kandilli Observatory and Earthquake Research Institute (KOERI) has a long history in seismic observation, which dates back to the installation of its first seismometers soon after the devastating Istanbul earthquake of 10 July 1894. For over a century, since the deployment of its first seismometer, the KOERI seismic network has grown steadily in time. In this article, we present the KOERI seismic network facilities as a data center for the seismological community, providing data and services through the European Integrated Data Archive (EIDA) and the Rapid Raw Strong-Motion (RRSM) database, both integrated in the Observatories and Research Facilities for European Seismology (ORFEUS). The objective of this article is to provide an overview of the KOERI seismic services within ORFEUS and to introduce some of the procedures that allow to check the health of the seismic network and the quality of the data recorded at KOERI seismic stations, which are shared through EIDA and RRSM.

scholarly journals Estimation of absolute stress in the hypocentral region of the 2019 Ridgecrest, California, earthquakes

2020 ◽  
Author(s):  
Yuri Fialko
Keyword(s):  
Seismic Data ◽  
Plate Tectonics ◽  
Active Faults ◽  
Active Regions ◽  
Seismogenic Zone ◽  
Shear Stresses ◽  
Strong Earthquakes ◽  
Frictional Strength ◽  
Tectonically Active ◽  
Weak Fault

Abstract Strength of the upper brittle part of the Earth's lithosphere controls deformation styles in tectonically active regions, surface topography, seismicity, and the occurrence of plate tectonics, yet it remains one of the least constrained and most debated quantities in geophysics. Seismic data (in particular, earthquake focal mechanisms) have been used to infer orientation of the principal stress axes. Here I show that the focal mechanism data can be combined with information from precise earthquake locations to place robust constraints not only on the orientation, but also on the magnitude of absolute stress at depth. The proposed method uses machine learning to identify quasi-linear clusters of seismicity associated with active faults. A distribution of the relative attitudes of conjugate faults carries information about the amplitude and spatial heterogeneity of the deviatoric stress and frictional strength in the seismogenic zone. The observed diversity of dihedral angles between conjugate faults in the Ridgecrest (California, USA) area that hosted a recent sequence of strong earthquakes suggests the effective coefficient of friction of 0.4-0.6, and depth-averaged shear stresses on the order of 25-40 MPa, intermediate between predictions of the "strong" and "weak" fault theories.

The Modern Swedish National Seismic Network: Two Decades of Intraplate Microseismic Observation

2021 ◽  
Author(s):  
Björn Lund ◽  
Peter Schmidt ◽  
Zaher Hossein Shomali ◽  
Michael Roth
Keyword(s):  
Crisis Management ◽  
Automatic Detection ◽  
Seismic Network ◽  
Assessment System ◽  
Continuous Data ◽  
Seismic Events ◽  
Primary System ◽  
Individual Choice ◽  
Active Structures ◽  
Event Definition

Abstract The Swedish National Seismic Network (SNSN) was modernized and rapidly expanded during the period 1998–2012. The network currently operates 68 permanent seismic stations, all with broadband instruments supplying real-time continuous data at 100 samples per second. Continuous data from 10 stations are shared with the international community via Orfeus, and approximately 10 stations of their individual choice are shared with institutes in neighboring countries (Denmark, Finland, Norway, and Germany). The SNSN uses the South Iceland Lowland (SIL) system as the primary system for automatic detection and event definition. In addition, an in-house system based on migration and stacking is used for automatic detection of small events, and implementations of SeisComP (SC) and Earthworm are used primarily for rapid detection of larger regional events. Global monitoring is performed with SC, using approximately 250 global stations, and we operate a continuous rapid risk assessment system serving Swedish crisis management authorities. Since the start of automatic processing in August 2000, the SNSN has recorded and interactively analyzed more than 171,000 seismic events, of which 10,700 were earthquakes with local magnitudes ranging from around −1 to 4.3. The microearthquake activity detected in the last 20 yr has significantly improved the identification and understanding of seismically active structures in Sweden.

Real-time seismology at UC Berkeley: The Rapid Earthquake Data Integration project

1996 ◽  
Vol 86 (4) ◽  
pp. 936-945 ◽  
Author(s):  
Lind S. Gee ◽  
Douglas S. Neuhauser ◽  
Douglas S. Dreger ◽  
Michael E. Pasyanos ◽  
Robert A. Uhrhammer ◽  
...  
Keyword(s):  
Data Integration ◽  
Strong Motion ◽  
Seismic Network ◽  
Prototype System ◽  
Earthquake Parameters ◽  
Moment Tensors ◽  
Automatic Information ◽  
Integration Project ◽  
Earthquake Data

Abstract The Rapid Earthquake Data Integration project is a system for the fast determination of earthquake parameters in northern and central California based on data from the Berkeley Digital Seismic Network and the USGS Northern California Seismic Network. Program development started in 1993, and a prototype system began providing automatic information on earthquake location and magnitude in November of 1993 via commercial pagers and the Internet. Recent enhancements include the exchange of phase data with neighboring networks and the inauguration of processing for the determination of strong-motion parameters and seismic moment tensors.

2019 Ridgecrest Earthquake Reveals Areas of Los Angeles That Amplify Shaking of High-Rises

2020 ◽  
Vol 91 (6) ◽  
pp. 3370-3380
Author(s):  
Monica D. Kohler ◽  
Filippos Filippitzis ◽  
Thomas Heaton ◽  
Robert W. Clayton ◽  
Richard Guy ◽  
...  
Keyword(s):  
Los Angeles ◽  
Strong Motion ◽  
Ground Level ◽  
Site Amplification ◽  
Seismic Network ◽  
Los Angeles Basin ◽  
High Rise ◽  
The North ◽  
South Central ◽  
San Fernando

Abstract The populace of Los Angeles, California, was startled by shaking from the M 7.1 earthquake that struck the city of Ridgecrest located 200 km to the north on 6 July 2019. Although the earthquake did not cause damage in Los Angeles, the experience in high-rise buildings was frightening in contrast to the shaking felt in short buildings. Observations from 560 ground-level accelerometers reveal large variations in shaking in the Los Angeles basin that occurred for more than 2 min. The observations come from the spatially dense Community Seismic Network (CSN), combined with the sparser Southern California Seismic Network and California Strong Motion Instrumentation Program networks. Site amplification factors for periods of 1, 3, 6, and 8 s are computed as the ratio of each station’s response spectral values combined for the two horizontal directions, relative to the average of three bedrock sites. Spatially coherent behavior in site amplification emerges for periods ≥3  s, and the maximum calculated site amplifications are the largest, by factors of 7, 10, and 8, respectively, for 3, 6, and 8 s periods. The dense CSN observations show that the long-period amplification is clearly, but only partially, correlated with the depth to basement. Sites with the largest amplifications for the long periods (≥3  s) are not close to the deepest portion of the basin. At 6 and 8 s periods, the maximum amplifications occur in the western part of the Los Angeles basin and in the south-central San Fernando Valley sedimentary basin. The observations suggest that the excitation of a hypothetical high-rise located in an area characterized by the largest site amplifications could be four times larger than in a downtown Los Angeles location.

A High-Resolution Seismic Catalog for the Initial 2019 Ridgecrest Earthquake Sequence: Foreshocks, Aftershocks, and Faulting Complexity

2020 ◽  
Vol 91 (4) ◽  
pp. 1971-1978 ◽  
Author(s):  
David R. Shelly
Keyword(s):  
High Resolution ◽  
Template Matching ◽  
Earthquake Sequence ◽  
Earthquake Catalog ◽  
Surface Rupture ◽  
Initial Portion ◽  
Multiple Fault ◽  
Fault Structures ◽  
Seismic Catalog ◽  
Complex Distribution

Abstract I use template matching and precise relative relocation techniques to develop a high-resolution earthquake catalog for the initial portion of the 2019 Ridgecrest earthquake sequence, from 4 to 16 July, encompassing the foreshock sequence and the first 10+ days of aftershocks following the Mw 7.1 mainshock. Using 13,525 routinely cataloged events as waveform templates, I detect and precisely locate a total of 34,091 events. Precisely located earthquakes reveal numerous crosscutting fault structures with dominantly perpendicular southwest and northwest strikes. Foreshocks of the Mw 6.4 event appear to align on a northwest-striking fault. Aftershocks of the Mw 6.4 event suggest that it further ruptured this northwest-striking fault, as well as the southwest-striking fault where surface rupture was observed. Finally, aftershocks of the Mw 7.1 show a highly complex distribution, illuminating a primary northwest-striking fault zone consistent with surface rupture but also numerous crosscutting southwest-striking faults. Aftershock relocations suggest that the Mw 7.1 event ruptured adjacent to the previous northwest-striking rupture of the Mw 6.4, perhaps activating a subparallel structure southwest of the earlier rupture. Both the northwest and southeast rupture termini of the Mw 7.1 rupture exhibited multiple fault branching, with particularly high rates of aftershocks and multiple fault orientations in the dilatational quadrant northeast of the northwest rupture terminus.

Aftershock Activity at Intermediate-Depth Earthquakes in Northern Chile Controlled by Plate Hydration

2020 ◽  
Author(s):  
Leoncio Cabrera ◽  
Sergio Ruiz ◽  
Piero Poli ◽  
Eduardo Contreras-Reyes ◽  
Renzo Mancini ◽  
...  
Keyword(s):  
Template Matching ◽  
Broad Band ◽  
Strong Motion ◽  
Seismic Source ◽  
Northern Chile ◽  
Aftershock Activity ◽  
Study Region ◽  
Abrupt Decrease ◽  
Intermediate Depth ◽  
The Impact

<p>We investigate the differences of the seismic source and aftershock activity using kinematic inversions and template matching respectively, for the six largest intraslab intermediate-depth earthquakes occurred in northern Chile (Mw ~6.3) since 2010 at depths between 90 and 130 km and recorded by dense strong-motion and broad-band seismic networks. In addition, we developed a thermal model using the finite element method in the study region with the aim of analyze the impact of temperature on seismic behavior as the oceanic plate subducts. Our results show that geometries of rupture zones are similar, with semi-axis for an elliptical patch approach about 5 km, and stress drop values between 7 and 30 MPa. On the other hand, the number of aftershocks exhibits clear differences, and their amount decreases with increasing the depth within the slab bounded by the 450 ºC isotherm, which represents a limit between a high-hydrated and a dry or low-hydrated region. Furthermore, mainshocks occur at distances from the top of the slab from 7 to 40 km, and all of them exhibit normal focal mechanisms suggesting that the extensional regimen deepens within the slab to the 700-750 ºC isotherm-depth. We suggest that in northern Chile the abrupt decrease of aftershocks in the lower part of the extensional regimen is caused by the absence of a hydrated slab at those depths.</p>

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