Abstract: Lamont-Doherty Cooperative Seismographic Network (LCSN) contributes to outreach in ways that are unique to its structure. It is unusual in using a variety of station keepers (college & university faculty, secondary school teachers, museums, nature conservancies etc.) to engage a wide variety of audiences and to reach out to large numbers of the general public. It also provides professional development and improved awareness among station operators who are not professional seismologists. All of this is an example of involving the community to extend seismic observations and thereby makes science accessible to the public. The records obtained from the stations are used to teach the students seismogram interpretation in the classroom as class exercises. The community is served by providing the general public and news media information about the local earthquakes. The LCSN now consists of 41 broadband seismographic stations in New York, New Jersey, Connecticut, Pennsylvania, Delaware, Maryland, New Hampshire and Vermont operated by 48 cooperating partners, with Lamont-Doherty Earth Observatory (LDEO) in Palisades, NY serving as the lead institution. The broadband stations of LCSN are distributed in diverse environments such as a 45 m deep natural cave (Howe Caverns, Cobleskill, NY), middle of the most dynamic city in the world (Central Park in Manhattan), and relatively quiet mountain sites at Adirondacks. The LCSN is also participating in the Advanced National Seismic System (ANSS) led by the U.S. Geological Survey for monitoring earthquakes in the Northeastern United States. The earthquakes that occur in the northeast U.S. are automatically detected and located in near-real time by using ANSS Quake Management System (AQMS), and are promptly reviewed by duty seismologists at the data collection center at LDEO. Earthquake information is reported in timely fashion in 24/7 operations together with NEIC in Golden, Colorado.
Slidecast:
https://vimeo.com/277556195
Abstract: GNSS-based earthquake early warning (EEW) algorithms are designed to complement existing point-source seismic systems by estimating fault-finiteness and unsaturated moment magnitude for the largest, most damaging earthquakes. Because large earthquakes are rare and geodetic monitoring is relatively young, however, demonstrating the differential accuracy of ground motion estimates from seismic and geodetic warnings is difficult. Here, we quantify the timeliness and accuracy of seismic and geodetic alerts by testing a suite of large (M>6) earthquakes worldwide. We replay strong motion seismic data from each earthquake through the ElarmS seismic EEW algorithm in simulated real-time and use those alerts to trigger the Geodetic Alarm System (G-larmS). At each epoch, G-larmS then determines static offsets from the GNSS data, and inverts the offsets for slip on several a priori fault geometries. We calculate the predicted shaking intensity (Modified Mercali Intensity, MMI) time series for each event using the point-source (ElarmS) and finite-fault (G-larmS) simulated real-time solutions at each epoch. Using an MMI-threshold approach to accurately characterize warning times, we classify true positive, true negative, false positive, and false negative alerts. We assess the success rate of both algorithms using these metrics and demonstrate the ground motion accuracy gained, if any, when using geodetic finite-fault solutions in real time.
Slidecast:
https://vimeo.com/277560024
Abstract: KOERI (Kandilli Observatory and Earthquake Research Institute) operates a seismic network in Marmara Sea region (NW Turkey) consisting of broadband and strong motion stations which has a reliable topology for regional EEW studies. In addition, a seismic network of 10 strong motion stations located close to the North Anatolian Fault crossing the Sea of Marmara is utilized in onsite threshold based studies. The Virtual Seismologist, PRESTo and ELARMS2 are regional EEW applications which are operational at KOERI data center. In addition, the onsite EEW system is running for more than a decade. The early warning signal is communicated to the appropriate servo shut-down systems of the recipient facilities, that automatically decide proper action based on defined alarm levels. Warning time is a critical parameters in EEW studies affected by the difference between the arrival time of the P-wave at the seismometer and the picking time. We have observed that the main reason for delays in detecting earthquake is packet size of the waveform data. We confirm that Seiscom3 platform requires some time to locate earthquakes and it needs to be optimized for EEW studies. Even with current settings Istanbul could have up to 20 seconds of warning times for a possible Marmara earthquake in case the rupture initiates in western part of the Sea of Marmara. The observations reveal that each algorithm has its own strengths and weakness. We give an example event (11-05-2015 04:16 GMT Gemlik bay event, M=3.9) that was detected successfully by the three algorithms shown. The first estimation time of the origin time by the three algortihms was between 14-16 second. This examples shows that despite the proximity of the event to Istanbul Metropoliatan area a couple of seconds of warning time remains. The second example shows the neccessty of EEW for distant earthquakes where we utilize the offhore 2014 North Aegean Sea Earthquake (Mw=6.9). Because of the sparse seismic network the first estimation of the epicenter was done in 35 seconds after the origin time of the earthquake prividing about 50 seconds leading time for Istanbul area located about 300 km away from the epicenter where the long period waves were causative for 10-15 minute shaking duration of high rise buildings.
Slidecast:
https://vimeo.com/277559865
Abstract: The Poroelastic Tomography experiment (PoroTomo) was conducted in March 2016 at Brady Hot Springs in Nevada. A key goal of the experiment is to understand how fluids travel from shallow aquifers, through faults and fractures, to deep geothermal reservoirs. As part of the effort, seismic, geodetic, and hydraulic technologies were tested and developed to fully characterize the rock mechanical properties. This abstract focuses on the application of seismic interferometry to image variations in seismic attenuation at the site. During the experiment, a large seismic array was deployed and recorded more than two weeks of continuous data, active vibroseis sweeps, local traffic noise, and the ambient seismic wavefield. In this study, we use several methods of seismic interferometry to investigate the site. We focus on two techniques: sweep interferometry uses the energy from the vibroseis sweeps as sources of high frequency energy; ambient noise correlation uses the energy of the ambient background field. In each case, the data recorded at one seismometer are correlated with the data recorded at another to obtain an estimate of the Green function between the two. The 238 geophones, concentrated over a 1.5 square-kilometer area, allow us to calculate nearly 30,000 paths, which we use to characterize the site and measure the localized wavefield. In collaboration with Ormat, pressures were changed during four stages of operation, including shutdown, followed by increased injection and pulsing. These changes caused measurable differences in the material properties beneath the site including the attenuation of seismic energy. We use two methods to study the changes in seismic attenuation at the site. The simplest is to measure the normalized amplitudes of the Green functions and to compare the values during each stage of operation. The second is to model the full waveform of the data, separating out contributions of Qs and Qp. Because P and S have different sensitivity to fluids in fractures and pores, the ratio of Qs/Qp is highly sensitive to the fluid saturation. We see anomalously high values of Qs/Qp at depth at the injection site and following fault boundaries. Over the course of the experiment, we observe large changes in attenuation across the site, bounded by structural features.
Poster:
WED.Monroe.1445.Matzel
Abstract: This study was done in the framework of the project on the Reinforcement of the Central American Tsunami Advisory Center (CATAC) to be established at INETER in Managua, Nicaragua. To emit reliable and sufficiently fast tsunami services for local tsunamis it is necessary to determine, in near real time, the appropriate fault model needed for the tsunami simulation in the last years, the use of the W-Phase for the Moment Tensor determination became viable in Central America because of the recent installation of 120s broadband stations and the establishment of fast and reliable data exchange between the Central American countries. To test the method, we have used a total of 26 earthquakes with moment magnitudes larger than 6.0 which have occurred, since 2012, in or near Central America. Among them were some larger earthquakes (e.g. 2012 Mw 7.3 off the Pacific Coast of El Salvador, 2017 Mw 8.2 near the Pacific Coast of Mexico, 2018 Mw 7.7 Swan Island North of Honduras) which have occurred at the Plate Boundaries off the Pacific and Caribbean coasts of Central America. These events have generated small tsunamis. The W-Phase inversions show a very stable nodal plane solution and accurate moment magnitudes at up to 10 degrees of epicenter distance, becoming available within a few minutes after origin time. We suggest using the W-phase inversion as a standard method for tsunami warning in Central America. We thank the Nicaraguan government and the Japanese International Cooperation Agency (JICA) for their support for the reinforcement of CATAC.
Slidecast:
https://vimeo.com/277560226
Abstract: The Nicaraguan Institute for Terrestrial Studies (Instituto Nicaraguense de Estudios Territoriales, INETER) received a grant to develop a mirror data center to host and serve COCONet data and metadata from UNAVCO and serve as a geodetic seamless archive center through web services (GSAC-WS). INETER, headquartered in Managua, Nicaragua is serving the western circum-Caribbean region. INETER provides monitoring, early warning, research, data, education, and support for all hazards in Nicaragua, especially earthquakes, tsunamis, volcanic unrest, landslides. INETER is hosting the Central American Tsunami Advisory Center (CATAC) and works on the development of Earthquake Early Warning (EEW) for Nicaragua and Central America and pretends to integrate the real-time use of GPS and GNSS data in these initiatives. We present information on the use of the data in the last years.
Slidecast:
https://vimeo.com/277562033
