Michael E. Pasyanos

Monitoring of strain release in central and northern California using broadband data

Systematic cataloguing of seismic moment, depth and mechanism of regional earthquakes down to magnitude M∼4 can now be achieved in close to real-time using data from sparse networks of digital broadband stations. The procedure we have developed relies on 3 independent methods for the determination of moment tensor, providing confidence limits on the results. We show the results of application to the seismicity in central and northern California for a one year period starting in March 1992 and illustrate how patterns of stress and strain release can now be monitored systematically and reliably in a timely fashion.

MOISE: A pilot experiment towards long term sea-floor geophysical observatories

We describe the scientific purposes and experimental set-up of an international deployment of a 3 component broadband seismometer package on the ocean floor in Monterey Bay which took place during the summer of 1997. Highlights of this experiment were the installation, performed using a remotely operated vehicle (ROV), the underwater connection of the different components of the package, and the successful retrieval of 3 months of broadband seismic and auxiliary data. Examples of recordings of teleseisms and regional earthquakes are presented and the background noise characteristics are discussed, in comparison with those of near-by broadband land sites, current-meter data from the vicinity of the ocean bottom package, as well as pressure data from deeper ocean sites.

Broadband analysis of the 21 September, 1993 Klamath Falls Earthquake Sequence

The source characteristics of the Klamath Falls earthquake sequence were estimated from broadband seismograms recorded by the Berkeley Digital Seismic Network (BDSN), TERRAscope, and western United States IRIS stations. Solutions were obtained for events ranging in size from Mw 3.8 to Mw 6.0. An empirical Greens function inverse approach was used to estimate kinematic source parameters of the two Mw 6.0 mainshocks. Both events were found to have ruptured northwest on adjacent segments of the Lake of the Woods system of normal faults. The two main-shocks abut where there is a pronounced 10° to 20° clockwise rotation of strike which may have initially acted as a barrier to a through-going Mw 6.2 event.

77 - The Rapid Earthquake Data Integration Project

This chapter focuses on the rapid earthquake data integration project. Interest in rapid access to earthquake information has grown enormously in the last few years. In addition to satisfying inquiries from the public and the media, rapid notification programs provide valuable information for earthquake disaster response. Recognizing the importance of this information for seismic hazard mitigation, efforts to design and implement systems to provide earthquake parameters in a timely manner have expanded over the last 10 years at both the regional and the national level. Similar to most automated earthquake processing systems, rapid earthquake data integration (REDI) operations can be divided into two major elements: event identification and event processing. The event identification element includes operations such as phase picking, event association, and event selection. The event processing element is separated into several stages, with each earthquake assessed for a particular type of processing based on its location and size. The Rapid Earthquake Data Integration System has been developed for the automated estimation of earthquake parameters using data from a sparse, broadband network. The system is designed on the basis of a staged hierarchy of processing, with the goal of providing control of the type and number of processes running at any time. The current processing capabilities include the determination of local and energy magnitude, peak ground motions, and the seismic moment tensor.