Calibration of the Regional Crustal Waveguide and the Retrieval of Source Parameters Using Waveform Modeling

2001 ◽  
pp. 1301-1338
Author(s):  
Chandan K. Saikia ◽  
Bradley B. Woods ◽  
H. K. Thio
Keyword(s):  
Source Parameters ◽  
Waveform Modeling

scholarly journals Fault reactivation by gas injection at an underground gas storage off the east coast of Spain

2019 ◽  
Author(s):  
Antonio Villaseñor ◽  
Robert B. Herrmann ◽  
Beatriz Gaite ◽  
Arantza Ugalde
Keyword(s):  
East Coast ◽  
Fault Plane ◽  
Source Parameters ◽  
Gas Injection ◽  
Focal Depth ◽  
Gas Storage ◽  
Fault Reactivation ◽  
Underground Gas Storage ◽  
Waveform Modeling ◽  
Valencia Trough

Abstract. During September–October of 2013 an intense swarm of earthquakes occurred off the east coast of Spain associated with the injection of the base gas in an offshore underground gas storage. Two weeks after the end of the injection operations, three moderate-sized earthquakes (Mw 4.0–4.1) occurred near the storage. These events were widely felt by the nearby population, leading to the indefinite shut-down of the facility. Here we investigate the source parameters (focal depth and mechanism) of the largest earthquakes in the sequence in order to identify the faults reactivated by the gas injection, and to help understand the processes that caused the earthquakes. Our waveform modeling results indicate that the largest earthquakes occurred at depths of 6–8 km beneath the sea floor, significantly deeper than the injection depth (~ 1800 m). Although we cannot undoubtedly discriminate the fault plane from the two nodal planes of the mechanisms, most evidence seems to favor a NW-SE striking fault plane. We propose that the gas injection reactivated unmapped faults in the Paleozoic basement, with regional orientation possibly inherited from the opening of the Valencia Trough.

Waveform modeling of the November 1987 Superstition Hills earthquakes

1989 ◽  
Vol 79 (2) ◽  
pp. 500-514 ◽  
Author(s):  
Allison L. Bent ◽  
Donald V. Helmberger ◽  
Richard J. Stead ◽  
Phyllis Ho-Liu
Keyword(s):  
Body Wave ◽  
Source Parameters ◽  
Strong Motion ◽  
Source Depth ◽  
Strong Motion Data ◽  
Waveform Modeling ◽  
Motion Data ◽  
Teleseismic Data ◽  
Slip Event ◽  
Double Event

Abstract Long-period body-wave data recorded at teleseismic distances and strong-motion data at Pasadena for the Superstition Hills earthquakes of 24 November 1987 are modeled to obtain the source parameters. We will refer to the event that occurred at 0153 UT as EQ1 and the event at 1316 UT as EQ2. At all distances the first earthquake appears to be a simple left-lateral strike-slip event on a fault striking NE. It is a relatively deep event with a source depth of 10 km. It has a teleseismic moment of 2.7 ×1025 dyne cm. The second and more complex event was modeled in two ways: by using EQ1 as the Green's function and by using a more traditional forward modeling technique to create synthetic seismograms. The first method indicated that EQ2 was a double event with both subevents similar, but not identical to EQ1 and separated by about 7.5 sec. From the synthetic seismogram study we obtained a strike of 305° for the first subevent and 320° for the second. Both have dips of 80° and rakes of 175°. The first subevent has a moment of 3.6 ×1025 which is half that of the second. We obtain depths of at least 6 km. The teleseismic data indicate a preferred subevent separation of 30 km with the second almost due south of the first, but the error bounds are substantial. This would suggest that the subevents occurred on conjugate faults. The strong-motion data at PAS, however, imply a much smaller source separation, with the sources probably produced by asperities.

scholarly journals Fault reactivation by gas injection at an underground gas storage off the east coast of Spain

Solid Earth ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 63-74
Author(s):  
Antonio Villaseñor ◽  
Robert B. Herrmann ◽  
Beatriz Gaite ◽  
Arantza Ugalde
Keyword(s):  
East Coast ◽  
Fault Plane ◽  
Source Parameters ◽  
Gas Injection ◽  
Focal Depth ◽  
Gas Storage ◽  
Fault Reactivation ◽  
Underground Gas Storage ◽  
Waveform Modeling ◽  
Valencia Trough

Abstract. During September–October of 2013 an intense swarm of earthquakes occurred off the east coast of Spain associated with the injection of the base gas in an offshore underground gas storage. Two weeks after the end of the injection operations, three moderate-sized earthquakes (Mw 4.0–4.1) occurred near the storage. These events were widely felt by the nearby population, leading to the indefinite shut-down of the facility. Here we investigate the source parameters (focal depth and mechanism) of the largest earthquakes in the sequence in order to identify the faults reactivated by the gas injection and to help understand the processes that caused the earthquakes. Our waveform modeling results indicate that the largest earthquakes occurred at depths of 6–8 km beneath the sea floor, significantly deeper than the injection depth (∼1800 m). Although we cannot undoubtedly discriminate the fault plane from the two nodal planes of the mechanisms, most evidence seems to favor a NW–SE-striking fault plane. We propose that the gas injection reactivated faults in the Paleozoic basement, with regional orientation possibly inherited from the opening of the Valencia Trough.

Sensor Orientation of Iranian Broadband Seismic Stations from P-Wave Particle Motion

2020 ◽  
Vol 91 (3) ◽  
pp. 1660-1671 ◽  
Author(s):  
Jochen Braunmiller ◽  
John Nabelek ◽  
Abdolreza Ghods
Keyword(s):  
Receiver Function ◽  
Function Analysis ◽  
Source Parameters ◽  
Transverse Component ◽  
P Wave ◽  
Seismic Stations ◽  
Waveform Modeling ◽  
Seismic Waveforms ◽  
Sensor Orientation ◽  
Receiver Function Analysis

Abstract Knowing the orientation of horizontal components of seismic sensors is important for many seismological applications such as waveform modeling, receiver function analysis, and shear-wave splitting. We determined the sensor orientations for broadband seismic stations belonging to the Iranian National Seismic Network (INSN) and the Iranian Seismological Center (IRSC) to enable such studies. For both networks, we have catalogs of event-based seismic waveforms of Iranian earthquakes. Sensor orientations were found by P-wave energy minimization on the transverse component and validated by long-period waveform modeling of events with well-constrained source parameters. We obtained stable sensor orientations for 28 (of 29) INSN sites and for 66 (of 92) IRSC sites. About 75% and 59% of all INSN and IRSC orientation estimates, respectively, are oriented within 15° of true north leaving many sites with largely misoriented sensors. We found temporally changing sensor orientations for 36 (of 121) sites.

Calibration of the Regional Crustal Waveguide and the Retrieval of Source Parameters Using Waveform Modeling

2001 ◽  
Vol 158 (7) ◽  
pp. 1301-1338 ◽  
Author(s):  
C. K. Saikia ◽  
B. B. Woods ◽  
H. K. Thio
Keyword(s):  
Source Parameters ◽  
Waveform Modeling

Source Characterization for Two Small Earthquakes in Dartmouth, Nova Scotia, Canada: Pushing the Limit of Single Station

2021 ◽  
Author(s):  
Miao Zhang ◽  
Min Liu ◽  
Alexandre Plourde ◽  
Feng Bao ◽  
Ruijia Wang ◽  
...  
Keyword(s):  
Nova Scotia ◽  
Model Building ◽  
Source Parameters ◽  
Velocity Model ◽  
Surface Velocity ◽  
Commercial Development ◽  
Near Surface ◽  
Waveform Modeling ◽  
Earthquake Source Parameters ◽  
Single Station

Abstract A pair of small earthquakes (MN 2.4 and 2.6, Earthquakes Canada) hit the city of Dartmouth, Nova Scotia, Canada, in early March 2020. The events were recorded by three seismic stations within 200 km, but only one station (HAL, <10  km) is close enough to offer high-quality broadband signals. In this study, we explore their source parameters using the nearest station through waveform modeling. A nearby quarry blast (MN 2.0) with known Global Positioning System coordinates is adopted as a reference for regional velocity model building and location calibration. We first build a half-space velocity model by estimating the P-S travel-time difference of the blast and determine the near-surface velocity through full-waveform modeling (i.e., comparing a set of synthetic waveforms with the observed blast). The velocity model is then used to evaluate the pair of earthquakes, in which waveform fitting and Rg/S amplitude ratios suggest source depths of ∼0.7  km. The epicenters of these two earthquakes are situated in a recently constructed commercial development. Lastly, single-station template matching finds no similar earthquakes near the hypocenters of the two events in the past decade and only three aftershocks in the following four months. Taking advantage of a ground-truth blast and waveform modeling, our study demonstrates the potential to construct a detailed regional velocity model and determine accurate earthquake source parameters in regions where only a single station is available.

Source parameters of Montana earthquakes (1925-1964) and tectonic deformation in the northern Intermountain Seismic Belt

1989 ◽  
Vol 79 (1) ◽  
pp. 31-50
Author(s):  
Diane I. Doser
Keyword(s):  
Main Shock ◽  
Source Parameters ◽  
Normal Fault ◽  
Strike Slip ◽  
Tectonic Deformation ◽  
Seismic Belt ◽  
Fault Movement ◽  
Waveform Modeling ◽  
Virginia City ◽  
First Motion

Abstract Waveform modeling and first motion analysis are used to determine the source parameters of six 5.8 ≦ M ≦ 6.8 earthquakes that occurred between 1925 and 1964 within the northern Intermountain Seismic Belt of Montana. Results of this study suggest that the 1925 Clarkston earthquake occurred along an oblique normal fault with a trend similar to the southern end of the Clarkston Valley fault. The two largest earthquakes of the 1935 Helena sequence occurred along right-lateral strike-slip faults with trends similar to the Bald Butte and Helena Valley faults. The 1947 Virginia City earthquake occurred along a northwest-southeast trending segment of the Madison fault. Movement at depth was along a fault with strike similar to that of the 1959 Hebgen Lake main shock. A reanalysis of a M = 6.0 aftershock of the 1959 Hebgen Lake sequence suggests the earthquake occurred at a depth of 8 km along a fault that is not seen at the surface. An M = 5.8 earthquake in 1964, located about 10 km from the 1959 aftershock, may have occurred along steeply dipping fault planes (48° to 80°) at depths of 8 to 14 km. Most events could be modeled as simple ruptures.

Aftershocks of the 1952 Kern County, California, earthquake sequence

1999 ◽  
Vol 89 (4) ◽  
pp. 1094-1108 ◽  
Author(s):  
Douglas Dreger ◽  
Brian Savage
Keyword(s):  
Sierra Nevada ◽  
Dynamic Range ◽  
Moment Tensor ◽  
Source Parameters ◽  
High Dynamic Range ◽  
Earthquake Sequence ◽  
Seismic Moment Tensor ◽  
Kern County ◽  
Waveform Modeling ◽  
First Motion

Abstract We have studied the seismograms recorded at the historic Berkeley (BRK) and Pasadena (PAS) stations for 20 aftershocks of the 21 July 1952 Kern County earthquake sequence. These events, in the magnitude range of MW 4.5 to 5.6, are too small to be studied teleseismically, yet they are important for better understanding the tectonics of the southern Sierra Nevada and the Tehachapi Mountains. On-scale recordings of moderate-sized events from this important earthquake sequence were first scanned, digitized, and then subjected to waveform modeling using a seismic moment tensor inverse procedure. In particular, the long-period, three-component Galitzen instrument at BRK and the 6-sec Wood-Anderson at PAS provided very high quality seismograms that could be analyzed in this manner. These two sites have been continuously operated from 1887 and 1927, respectively, and both are current sites of state-of-the-art broadband, high dynamic range instrumentation. First-motion polarities reported by Bath and Richter (1958) were used as additional constraints in the estimation of source parameters. There is considerable variability in the three-component seismograms of the 1952 aftershocks, which in turn result in a diversity of focal mechanisms. The majority of the solutions are northwest-striking reverse mechanisms that likely occurred on various mapped thrust faults in the hanging block of the mainshock. There are several events with northeast-striking, left-lateral mechanisms that are consistent with the strike of the White Wolf fault, as well as several normal slip events. The results of this study indicate that there are a variety of active fault structures adjacent to the White Wolf, Garlock and San Andreas faults in this region.

gWFM: A Global Catalog of Moderate-Magnitude Earthquakes Studied Using Teleseismic Body Waves

2020 ◽  
Vol 92 (1) ◽  
pp. 212-226
Author(s):  
Sam Wimpenny ◽  
C. Scott Watson
Keyword(s):  
Moment Tensor ◽  
Source Parameters ◽  
Body Waves ◽  
Earthquake Catalog ◽  
Centroid Moment Tensor ◽  
Waveform Modeling ◽  
Crustal Earthquakes ◽  
Earthquake Source Parameters ◽  
Double Couple ◽  
Moderate Magnitude

Abstract We present a compilation of 2131 high-fidelity mechanisms and centroid depths of moderate-magnitude earthquakes derived using synthetic body-waveform modeling (the Global Waveform-Modelled Earthquake Catalog v1.0—gWFM), which can be visualized and downloaded online (see Data and Resources). In this article, we describe the methods used to construct the gWFM and present a comparison between the earthquake depths and focal mechanisms in the gWFM with those derived by the International Seismological Centre, Global Centroid Moment Tensor (Global CMT) project, and the U.S. Geological Survey (USGS) W-phase, as well as 60 events studied using geodesy. We find that 20%–30% of the earthquakes in routine global catalogs have depths that differ by more than 10 km from those in the gWFM. Shallow-crustal earthquakes of Mw 5–6 are typically the worst located in depth by routine catalogs. Over 90% of the earthquakes in the gWFM are within ±15° in strike, ±5° in dip, and ±15° in rake of the Global CMT and USGS W-phase best double-couple moment tensor solutions. However, the mechanisms of shallow Mw 5–6 earthquakes in the routine catalogs can be inaccurate, due to the well-known insensitivity of long-period surface waves to the vertical dip-slip components of the moment tensor. The gWFM is an archive of well-constrained earthquake source parameters, though it will continue to update as new earthquake mechanisms and depths are published, thereby remaining an up-to-date research tool.

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