USGS Near‐Real‐Time Products—and Their Use—for the 2018 Anchorage Earthquake

2019 ◽  
Vol 91 (1) ◽  
pp. 94-113 ◽  
Author(s):  
Eric M. Thompson ◽  
Sara K. McBride ◽  
Gavin P. Hayes ◽  
Kate E. Allstadt ◽  
Lisa A. Wald ◽  
...  

Abstract In the minutes to hours after a major earthquake, such as the recent 2018 Mw 7.1 Anchorage event, the U.S. Geological Survey (USGS) produces a suite of interconnected earthquake products that provides diverse information ranging from basic earthquake source parameters to loss estimates. The 2018 Anchorage earthquake is the first major domestic earthquake to occur since several new USGS products have been developed, thus providing an opportunity to discuss the newly expanded USGS earthquake product suite, its timeliness, performance, and reception. Overall, the products were relatively timely, accurate, well received, and widely used, including by the media, who used information and visualizations from many products to frame their early reporting. One downside of the codependence of multiple products is that reasonable updates to upstream products (e.g., magnitude and source characterization) can result in significant changes to downstream products; this was the case for the Anchorage earthquake. However, the coverage of strong‐motion stations and felt reports was so dense that the ShakeMap and downstream products were relatively insensitive to changes in magnitude or fault‐plane orientation once the ground‐motion data were available. Shaking and loss indicators initially fluctuated in the first hour or two after the earthquake, but they stabilized quickly. To understand how the products are being used and how effectively they are being communicated, we analyze the media coverage of USGS earthquake products. Most references to USGS products occurred within the first 48 hr after the event. The lack of coverage after 48 hr could indicate that longer‐term products addressing what actions the USGS is taking or what early reconnaissance has revealed might be useful for those people wanting additional information about the earthquake.

1992 ◽  
Vol 8 (4) ◽  
pp. 529-554 ◽  
Author(s):  
Paolo Capuano ◽  
Paolo Gasparini ◽  
Marcello Peronaci ◽  
Roberto Scarpa

Strong motion data from significant earthquakes recorded in the Apennines, Italy, over the period 1975-1985 are analyzed in this paper. We have developed an inversion procedure for studying accelerometer data in the frequency domain and for estimating some basic earthquake source parameters. Spectral models, characterized by a single or two corner frequencies have been tested by utilizing variable high frequency decay parameters to simulate a variety of attenuation and rupture models. A best fit of available data was obtained for mid-crustal Q values around 100-250, decay parameter γ in the range 2-3 and a model consisting of two corner frequencies. This last result is explained in part by the source complexity and in part by a spectral shape contaminated by resonance peaks. The data analyzed are confined to the seismic moment range 1015 - 1019 Nm, with stress drops 100-200 bars (1 bar = 0.1M Pa). We have compared results with scaling laws of source parameters for regions having different tectonic regimes or displaying seismic patterns such as swarms. A trend towards an asymptotic value for regions with extensional tectonics of stress drops around 200 bars is observed.


1989 ◽  
Vol 79 (2) ◽  
pp. 500-514 ◽  
Author(s):  
Allison L. Bent ◽  
Donald V. Helmberger ◽  
Richard J. Stead ◽  
Phyllis Ho-Liu

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.


Author(s):  
Hernando Tavera ◽  
Bertrand Delouis ◽  
Arturo Mercado ◽  
David Portugal

Abstract The Loreto earthquake of 26 May 2019 occurred below the extreme northeast part of Peru at a depth of 140 km within the subducting Nazca plate at a distance of 700 km from the trench Peru–Chile. The orientation of the seismic source was obtained from waveform inversion in the near field using velocity and strong-motion data. The rupture occurred in normal faulting corresponding to a tensional process with T axis oriented in east–west direction similar to the direction of convergence between the Nazca and South America plates. The analysis of the strong-motion data shows that the levels of ground shaking are very heterogeneous with values greater than 50 Gal up to distances of 300 km; the maximum recorded acceleration of 122 Gal at a distance of 100 km from the epicenter. The Loreto earthquake is classified as a large extensional event in the descending Nazca slab in the transition from flat-slab geometry to greater dip.


2016 ◽  
Vol 83 (2) ◽  
pp. 867-883 ◽  
Author(s):  
A. Joshi ◽  
Monu Tomer ◽  
Sohan Lal ◽  
Sumer Chopra ◽  
Sandeep Singh ◽  
...  

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