Abstract: In September of 2017 Puerto Rico experienced the devastation of two hurricanes, Irma and Maria. On January 10, 2018 a 7.6 Mw earthquake near Honduras promoted the activation of the tsunami advisory for Puerto Rico. These three recent events have changed the life of Puerto Ricans and have raised an urgency to be better prepared in case of natural disasters that may be affecting our welfare at any time. The Puerto Rico Seismic Network Education and Outreach department (E&O) serves the entire Island community for earthquakes and tsunamis education and preparedness. The E&O department, impacts thousands of people in our community not including larger annual exercise (ShakeOut and Caribe Wave) through talks, conferences, workshops and fairs. From September 20th until December the requests for talks and conferences decreased to almost zero due to the devastation of the Island. The lack of power and water supply, inaccessible roads, collapsed bridges, floods, and lack of communications affected our activities. This, plus the long recovery process changed the priorities of our citizens. By January 2018, the raised awareness of the fragility of our wellbeing and partial recovery from the hurricanes, caused a significant increase in demand for E&O services with many communities indicating a raised urgency to be prepared and take the right actions now, before another disaster strikes. A second peak in requests occurred after the tsunami advisory level message issued for Puerto Rico. Despite outreach efforts to present tsunami and earthquake information to the community through talks, web page, educational material, the media, among others, the community became aware that they have not taken the time to learn and understand the tsunami protocols. Here we present the effects of natural disasters on community demand for E&O services and methods employed to take advantage of the receptiveness of our citizens in order to understand these natural phenomena.
Slidecast:
https://vimeo.com/278230002
Abstract: The Peninsula section of the San Andreas Fault is an obvious and significant hazard to San Francisco and peninsula cities, however the history past events on the SAF on the peninsula is poorly known. We opened a paleoseismic site at Lake Merced, within the city of San Francisco. The lake may be an asymmetrical pull-apart basin with the NSAF system. We conducted a coring and geophysical investigation to test the site for its potential for development of a long-term earthquake history. We collected four main long cores of 5-7 meters, and 4 overlapping cores. The lake has a record of turbidites that dominate the 3-4 m lacustrine gyttja section, overlying a sharp contact with shelly-sandy estuarine material below. The lake record above the contact includes 15 turbidites spanning ~ 2000 years. The turbidites for the most part have sharp bases, some with load features, and fining upward sequences that can be correlated around the lake. Their individual thicknesses show little relation to stream input. Breaching of the spit at the north end of the lake has occurred in historic times, but appears to have drained the lake without open access to the sea, suggesting the event beds are not externally sourced. Radiocarbon dating thus far shows the uppermost 2 events to include bomb carbon, and occurred in ~1955-57 and 1976-1996. These two beds may relate to a local earthquake near the lake in 1957, and the Loma Prieta earthquake of 1989. The third event is thick, and has a model age of ~ 1890 (1860-1930), likely the 1906 event, supported by anthropogenic Pb content. Events dated at ~ 1720, and ~ 1580 underlie the 1906 bed, similar in age to those reported for the penultimate events on the North Coast and Peninsular NSAF segments respectively. The remaining event bed ages appear mostly compatible with turbidites at Noyo Canyon, and the Vedanta Marsh, suggesting that likely 6 and possibly 11 North Coast segment ruptures extended to the Peninsula segment.
Slidecast:
https://vimeo.com/278230545
Abstract: Response spectra for use in design of new buildings are presented in ASCE 7-16. The ASCE 7-16 design response spectra are to be based on both a probabilistic evaluation and a deterministic evaluation. For the evaluating design deterministic maximum component (RotD100) spectra, National Earthquake Hazards Reduction Program (NEHRP) factors as recommended in ASCE 7-16 are to be applied to the RotD50 spectra; these factors are based on RotD100/RotD50 ratios obtained using the 2008 Next Generation Attenuation (NGA-West1) database. Additional studies based on the NGA-West2 database have resulted in several directivity models to account for directionality effects, namely Shahi-Baker (2013), Bayless-Somerville (2013), Spudich-Chiou (2013), and Watson Lamprey (2013). In recent practice in Los Angeles for evaluating directionality effects, a factor computed as the average of the Shahi-Baker and Bayless-Somerville factors has been applied to both the probabilistic and deterministic response spectra. This paper investigates the use of the directionality factors, in particular considering application of various rupture scenarios for the deterministic response spectra computed using the Bayless-Somerville method. An event on the Anacapa-Dume/Santa Monica combined fault was used to compute the deterministic response spectrum for an example site in the Century City District in Los Angeles, California. The resulting response spectra are compared to evaluate which rupture scenario should be applied for application to the deterministic response spectrum.
Slidecast:
https://vimeo.com/278564374
Abstract: In September 2017 the Northeastern Caribbean was battered by two Category 5 hurricanes, Irma and Maria. While Irma’s destructive forces were most devastating to Antigua & Barbuda, Anguilla, the British Virgin Islands, the Northern US Virgin Islands, Maria completed the destruction of the region with its fury focusing on Dominica, St. Croix (USVI) and Puerto Rico. There are many parallels between these hurricanes and earthquakes and tsunamis which are examined in the hopes of improving resilience to the more infrequent geophysical events. Issues like onset, duration, impact and damage, response and recovery will be addressed. Unlike Earthquakes and Tsunamis which are no notice/extremely rapid onset events, the hurricanes provided advance warning giving some time to take safety measures. In the case of the hurricanes, the winds blew for hours limiting any type of emergency response, in this case there is closer tie in with tsunamis rather than earthquakes. The images of the damage along the coastlines due to storm surge and river flooding recall scenes from recent tsunamis and are a powerful reminder of the destructive forces of water. One of the most significant impacts from the hurricanes was the sudden complete loss of power, communication and road connectivity. In the response and recovery phase personal, community and institutional empowerment has been recognized. Although the Puerto Rico Seismic Network was left with limited earthquake data due to the loss of all but 4 stations after Maria, it used the resources it had to serve as a focal point for emergency communications. Once again the elderly and those with less economic resources have been the most vulnerable. Debris has been a major issue, but probably small in comparison with what we would be facing from an earthquake and tsunami. The presentation will focus on how the Irma and Maria experience can be used to educate also on earthquakes and tsunamis and build back better, more resilient.
Slidecast:
https://vimeo.com/278530081
Abstract: A Century Later is an historical novel based on the life of a Catholic nun who died in the San Antonio Hospital in Mayagüez, Puerto Rico, as a consequence of the October 11, 1918, M 7.3 earthquake. During 100 years her story and tragedy were unknown. The author, Fernando Bayrón Toro, a professor, historian, writer, political scientist and lawyer, researched archives in Puerto Rico and Europe for this work. The novel includes many facts and photographs from the earthquake and tsunami and helps clarify the earthquake and tsunami impact. In Mayagüez, for example, one of the oft asked questions is where did the tsunami reach when it flooded the city. Gleaming over maps and plans and in discussion with scientists he helps answer this question. While the novel makes for interesting reading, it also serves the purpose of sensitizing and educating the reader on earthquakes and tsunamis. People reading this book hopefully will be more likely to take proactive measures to prepare for such an event. Earthquake and tsunami awareness also is increased thru the public presentations on the book.
Slidecast:
https://vimeo.com/278532092
Abstract: A software tool has been developed to utilize time-frequency representations (TFR) of time domain signals based on the continuous wavelet transform (CWT) where the seismogram is converted into a 2D map of wavelet scale (analogous to Fourier period) as a function of time. The 2D map is an intuitive description of the signal since major signal arrivals in the CWT can often be seen correlating with inferred signals in the seismogram and separated from bands of noise. The tool allows the choice of simple block thresholding schemes analogous to bandpass filtering to remove obvious noise bands. The remainder can further be analyzed by interactively choosing irregular blocks that represent different parts of the signal for removal or for separate analysis. Inverse transforming the processed CWT yields signals with substantial Signal-to-Noise (SNR) improvement. The tool is used to process explosion data recorded by the IRIS Community Wavefields experiment in early July 2016. Four explosions (909kg, 455kg, 2 at 228kg) at 3 different shot points (ranges of ~16km, 35km, and 65km) from the experiment were detonated by the Air Force Research Laboratory to examine local wave propagation and signal characteristics. Interactive block thresholding incorporating the Morlet wavelet significantly improves the SNR for 909kg and 455kg shots. Three dominant wavetrains are evident in the data including the low scale (high frequency) P wave and 2 dispersed higher and fundamental mode surface wave trains. Each wave train can be extracted from the CWT map separately for further modeling, such as for group and phase velocity dispersion. The smaller shots are usually lost in the ‘noise’ that sometimes include swarms of local induced earthquakes, easily seen in the CWT map. Preprocessing the data to improve the SNR also improves array beamforming at high frequency for dense arrays constructed from subsets of nodal stations of the IRIS experiment.
Slidecast:
https://vimeo.com/278567479
