D. D. Given

Frequency‐Dependent Seismic Attenuation within the Hispaniola Island Region of the Caribbean Sea

Wedetermine frequency-dependentattenuation1=Qffor theHispanio- la region using direct S and Lg waves over five distinct passbands from 0.5 to 16 Hz. Data consist of 832 high-quality vertical and horizontal component waveforms recordedonshort-period andbroadbandseismometersfromthedevastating12January 2010 M 7.0 Haiti earthquake and the rich sequence of aftershocks. For the distance range 250-700 km, we estimate an average frequency-dependent Qf �� 224�� 27� f 0:64�� 0:073� using horizontal components of motion and note that Qf� estimated with Lg at regional distances is very consistent across vertical and horizontal components. We also determine a Qf �� 142�� 21� f 0:71�� 0:11� for direct S waves at local distances, ≤100 km. The strong attenuation observed on both vertical and horizontal components of motion is consistent with expectations for a tectonically active region. Online Material: Figures of filtered and broadband data, Lg- and S-wave ampli- tudes, and apparent frequency-dependent Q, and tables of earthquake and station parameters.

Earthquake Early Warning ShakeAlert System: Testing and Certification Platform

Earthquake early warning systems provide warnings to end users of incoming moderate to strong ground shaking from earthquakes. An earthquake early warning system, ShakeAlert, is providing alerts to beta end users in the western United States, specifically California, Oregon, and Washington. An essential aspect of the earthquake early warning system is the development of a framework to test modifications to code to ensure functionality and assess performance. In 2016, a Testing and Certification Platform (TCP) was included in the development of the Production Prototype version of ShakeAlert. The purpose of the TCP is to evaluate the robustness of candidate code that is proposed for deployment on ShakeAlert Production Prototype servers. TCP consists of two main components: a real‐time in situ test that replicates the real‐time production system and an offline playback system to replay test suites. The real‐time tests of system performance assess code optimization and stability. The offline tests comprise a stress test of candidate code to assess if the code is production ready. The test suite includes over 120 events including local, regional, and teleseismic historic earthquakes, recentering and calibration events, and other anomalous and potentially problematic signals. Two assessments of alert performance are conducted. First, point‐source assessments are undertaken to compare magnitude, epicentral location, and origin time with the Advanced National Seismic System Comprehensive Catalog, as well as to evaluate alert latency. Second, we describe assessment of the quality of ground‐motion predictions at end‐user sites by comparing predicted shaking intensities to ShakeMaps for historic events and implement a threshold‐based approach that assesses how often end users initiate the appropriate action, based on their ground‐shaking threshold. TCP has been developed to be a convenient streamlined procedure for objectively testing algorithms, and it has been designed with flexibility to accommodate significant changes in development of new or modified system code. It is expected that the TCP will continue to evolve along with the ShakeAlert system, and the framework we describe here provides one example of how earthquake early warning systems can be evaluated.

Frequency‐Dependent Seismic Attenuation within the Hispaniola Island Region of the Caribbean SeaFrequency‐Dependent Seismic Attenuation within the Hispaniola Island Region of the Caribbean Sea

Wedetermine frequency-dependentattenuation1=Qffor theHispanio- la region using direct S and Lg waves over five distinct passbands from 0.5 to 16 Hz. Data consist of 832 high-quality vertical and horizontal component waveforms recordedonshort-period andbroadbandseismometersfromthedevastating12January 2010 M 7.0 Haiti earthquake and the rich sequence of aftershocks. For the distance range 250-700 km, we estimate an average frequency-dependent Qf �� 224�� 27� f 0:64�� 0:073� using horizontal components of motion and note that Qf� estimated with Lg at regional distances is very consistent across vertical and horizontal components. We also determine a Qf �� 142�� 21� f 0:71�� 0:11� for direct S waves at local distances, ≤100 km. The strong attenuation observed on both vertical and horizontal components of motion is consistent with expectations for a tectonically active region. Online Material: Figures of filtered and broadband data, Lg- and S-wave ampli- tudes, and apparent frequency-dependent Q, and tables of earthquake and station parameters.