Real-Time Estimation of Earthquake Magnitude for Seismic Early Warning (original) (raw)
Related papers
AGU Fall Meeting …, 2009
Modern technology allows real-time seismic monitoring facilities to evolve into earthquake early warning (EEW) systems, capable of reducing deaths, injuries, and economic losses, as well as of speeding up rescue response and damage recovery. The objective of an EEW system is to estimate in a fast and reliable way the earthquake's damage potential, before the strong shaking hits a given target.
A prototype system for earthquake early-warning and alert management in southern Italy
Bulletin of Earthquake Engineering, 2010
The Irpinia Seismic Network (ISNet) is deployed in Southern Apennines along the active fault system responsible for the 1980, November 23, M s 6.9 Campania–Lucania earthquake. It is set up by 28 stations and covers an area of about 100 × 70 km2. Each site is equipped with a 1-g full-scale accelerometer and a short-period velocimeter. Due to its design characteristics, i.e., the wide dynamic range and the high density of stations, the ISNet network is mainly devoted to estimating in real-time the earthquake location and magnitude from low- to high- magnitude events, and to providing ground-motion parameters values so to get some insights about the ground shaking expected. Moreover, the availability of high-quality of data allows studying the source processes related to the seismogenetic structures in the area. The network layout, the data communication system and protocols and the main instrumental features are described in the paper. The data analysis is managed by Earthworm software package that also provides the earthquake location while custom software has been developed for real-time computation of the source parameters and shaking maps. Technical details about these procedures are given in the article. The data collected at the ISNet stations are available upon request.
Exploring the feasibility of a nationwide earthquake early warning system in Italy
Journal of Geophysical Research: Solid Earth, 2015
When accompanied by appropriate training and preparedness of a population, Earthquake Early Warning Systems (EEWS) are effective and viable tools for the real-time reduction of societal exposure to seismic events in metropolitan areas. The Italian Accelerometric Network, RAN, which consists of about 500 stations installed over all the active seismic zones, as well as many cities and strategic infrastructures in Italy, has the potential to serve as a nationwide early warning system. In this work, we present a feasibility study for a nationwide EEWS in Italy obtained by the integration of the RAN and the software platform PRobabilistic and Evolutionary early warning SysTem (PRESTo). The performance of the RAN-PRESTo EEWS is first assessed by testing it on real strong motion recordings of 40 of the largest earthquakes that have occurred during the last 10 years in Italy. Furthermore, we extend the analysis to regions that did not experience earthquakes by considering a nationwide grid of synthetic sources capable of generating Gutenberg-Richter sequences corresponding to the one adopted by the seismic hazard map of the Italian territory. Our results indicate that the RAN-PRESTo EEWS could theoretically provide for higher seismic hazard areas reliable alert messages within about 5 to 10 s and maximum lead times of about 25 s. In case of large events (M > 6.5), this amount of lead time would be sufficient for taking basic protective measures (e.g., duck and cover, move away from windows or equipment) in tens to hundreds of municipalities affected by large ground shaking.
A threshold-based earthquake early warning using dense accelerometer networks
Geophysical Journal International, 2010
Most earthquake early warning systems (EEWS) developed so far are conceived as either `regional' (network-based) or `on-site' (stand-alone) systems. The recent implementation of nationwide, high dynamic range, dense accelerometer arrays makes now available, potentially in real time, unsaturated waveforms of moderate-to-large magnitude earthquakes recorded at very short epicentral distances (<10-20 km). This would allow for a drastic increase of the early warning lead-time, for example, the time between the alert notification and the arrival time of potentially destructive waves at a given target site. By analysing strong motion data from modern accelerograph networks in Japan, Taiwan and Italy, we propose an integrated regional/on-site early warning method, which can be used in the very first seconds after a moderate-to-large earthquake to map the most probable damaged zones. The method is based on the real-time measurement of the period (τc) and peak displacement (Pd) parameters at stations located at increasing distances from the earthquake epicentre. The recorded values of early warning parameters are compared to threshold values, which are set for a minimum magnitude 6 and instrumental intensity VII, according to the empirical regression analyses of strong motion data. At each recording site the alert level is assigned based on a decisional table with four alert levels defined upon critical values of the parameters Pd and τc, which are set according to the error bounds estimated on the derived prediction equations. Given a real time, evolutionary estimation of earthquake location from first P arrivals, the method furnishes an estimation of the extent of potential damage zone as inferred from continuously updated averages of the period parameter and from mapping of the alert levels determined at the near-source accelerometer stations. The off-line application of the method to strong motion records of the Mw 6.3, 2009 Central Italy earthquake shows a very consistent match between the rapidly predicted (within a few seconds from the first recorded P wave) and observed damage zone, the latter being mapped from detailed macroseismic surveys a few days after the event. The proposed approach is suitable for Italy, where, during the last two decades, a dense network of wide dynamic-range accelerometer arrays has been deployed by the Department of Civil Protection (DPC), the Istituto Nazionale di Geofisica e Vulcanologia (INGV) and other regional research agencies.
Earthquake early warning system in southern Italy: Methodologies and performance evaluation
Geophysical Research Letters, 2009
[1] We investigate the effect of extended faulting processes and heterogeneous wave propagation on the early warning system capability to predict the peak ground velocity (PGV) from moderate to large earthquakes occurring in the southern Apennines (Italy). Simulated time histories at the early warning network have been used to retrieve early estimates of source parameters and to predict the PGV, following an evolutionary, probabilistic approach. The system performance is measured through the Effective Lead-Time (ELT), i.e., the time interval between the arrival of the first S-wave and the time at which the probability to observe the true PGV value within one standard deviation becomes stationary, and the Probability of Prediction Error (PPE), which provides a measure of PGV prediction error. The regional maps of ELT and PPE show a significant variability around the fault up to large distances, thus indicating that the system's capability to accurately predict the observed peak ground motion strongly depends on distance and azimuth from the fault.
On the estimation of seismic intensity in earthquake early warning systems
Geophysical Research Letters, 2008
The infamous Tokai Earthquake, which by some accounts is overdue, is expected to be a magnitude ! 8 event that will cause unprecedented damage in regions of Japan. To mitigate hazards from large earthquakes in Japan, an earthquake early warning (EEW) system was developed that is able to determine hypocentral locations from P-arrival data within a few seconds and then transmit this information before the onset of large ground motions from the later arrival of S-waves. We introduced a new source parameter for seismic intensity magnitude that can be estimated from the real-time P-wave data during the early stages of fault rupture for most earthquakes M ! 6.5. The use of this parameter results in a significant improvement in the uncertainty in the estimated seismic intensity compared to estimates derived from earthquake magnitude. A pre-established relation between the P-and Swave seismic intensity therefore enables an EEW system to issue a rapid and reasonably reliable prediction of the amount of ground shaking that may be expected from the damaging S-waves.
Soil Dynamics and Earthquake Engineering, 2011
PRESTo (PRobabilistic and Evolutionary early warning SysTem) is a software platform for regional earthquake early warning that integrates recently developed algorithms for real-time earthquake location and magnitude estimation into a highly configurable and easily portable package. The system is under active experimentation in Southern Italy on the Irpinia Seismic Network (ISNet), which is deployed in a seismogenic area that is expected to produce a large earthquake within the next 20 years. In this paper we describe the architecture of the system and test its performances using both small earthquakes (M o3.5) recorded at the ISNet and a large event recorded in Japan, through a simulation mode. The results show that, when a dense seismic network is deployed in the fault area, PRESTo can produce reliable estimates of earthquake location and size within 5-6 s from the event origin. Each estimate is provided as a probability density function, with an uncertainty that typically decreases with time: a stable solution is generally reached within 10 s from the origin.