Options
Imoto, Masajiro
Loading...
Preferred name
Imoto, Masajiro
5 results
Now showing 1 - 5 of 5
- PublicationOpen AccessPerformance of a seismicity model based on three parameters for earthquakes (M ≥ 5.0) in Kanto, central Japan(2008-08)
; ;Imoto, M.; National Research Institute for Earth Science and Disaster Prevention, Ibaraki-ken, JapanWe constructed a model of earthquakes (M ≥ 5.0) in Kanto, central Japan, based on three parameters: the a and b values of the Gutenberg-Richter relation, and the ν- parameter of changes in mean event size. In our method, two empirical probability densities for each parameter, those associated with target events (conditional density distributions) and those not associated with them (background density distributions), are defined and assumed to have a normal distribution. Therefore, three parameters are transformed by appropriate relations so that new parameters are normally distributed. The retrospective analysis in the learning period and the prospective test of testing period demonstrated that the proposed model performs better by about 0.1 units in terms of the information gain per event than the value summed up with those of the three parameters. The results are confirmed by a simulation with randomly selected model parameters.114 178 - PublicationOpen AccessProbabilistic Estimation of Earthquake Growth to a Large One in an Earthquake Early Warning System: Re-Estimation for the Nankai Trough Region(2007-05-31)
; ; ; ; ;Iwata, T.; Instiute of Statistical Mathematics, Tokyo, Japan ;Imoto, M.; National Research Institute for Earth Science and Disaster Prevention, Japan ;Horiuchi, S.; National Research Institute for Earth Science and Disaster Prevention, Japan ;Ogata, Y.; Instiute of Statistical Mathematics, Tokyo, Japan; ; ; ; ; ; ;Cocco, Massimo; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Console, Rodolfo; INGV, Rome, Italy ;Wiemer, Stephan; ETH, Zurich, Switzerland; ; Probabilistic Estimation of Earthquake Growth to a Large One in an Earthquake Early Warning System: Re-Estimation for the Nankai Trough Region108 175 - PublicationOpen AccessAnalysis of short time-space range seismicity patterns in Italy(1997-08)
; ; ; ; ;Di Luccio, F.; Istituto Nazionale di Geofisica, Roma, Italy ;Console, R.; Istituto Nazionale di Geofisica, Roma, Italy ;Imoto, M.; National Re.learch Institute for Earth Science and Di.la.lter Prevention, Tsukuba-shi, Ibaraki-ken, 305, Japan ;Murru, M.; Istituto Nazionale di Geofisica, Roma, Italy; ; ; In our paper we analyze the data base obtained from the observations of the Italian Seismological Network from 1975 to 1994 by using a simple algotithm to determine the rate of occurrence of seismic events condi- tioned by the occurrence of previous events after a period of quiescence. The number of observed pairs of earthquakes depends on several parameters: the magnitude threshold of the two events, the spatial and tempo- ral ranges of the quiescence period preceding the first (non aftershock) event, the time elapsed between the first and the second events and the spatial dimension of the alarm area. The Akaike information criterion was adopted to assess the optimal set of space-time parameters used in the definition of non-aftershock (events not related to a stronger previous one). In Central Italy, the rate of M ³3.8 earthquakes preceded by at least one M ~ 3.3 foreshock within 14.1 km and 2 days is 30%, while the rate of M ~ 3.3 earthquakes followed by a M ~ 3.8 mainshock in the same space time range is 7%. We observed that the probability that an earthquake of magnitude MI will be followed by an earthquake of magnitude M2 (success rate) fits the law log À = a+b (Mi -M2) with b approximately equal to l. By computing the success rate for given values of magnitude threshold of the first and the second events over a dense grid of spatial coordinates, we obtained maps of this feature over the investigated area. The results of this process document variations larger than a factor of five in the success rate over the Italian territory.206 385 - PublicationRestrictedShort Term and Short Range Seismicity Patterns in Different Seismic Areas of the World(1999)
; ; ; ; ; ;Console, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Di Luccio, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Murru, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Imoto, M.; National Institute for Earth Science and Disaster Prevention, Tennodai 3-1, Tsukuba-shi, Ibaraki-ken, 305 Japan ;Stavrakakis, G.; National Observatory of Athens, Geodynamic Institute, PO Box 20048, GR-11810, Athens, Greece; ; ; ; The aim of this work is to quantitatively set up a simple hypothesis for occurrence of earthquakes conditioned by prior events, on the basis of a previously existing model and the use of recent instrumental observations. A simple procedure is presented in order to determine the conditional probability of pairs of events (foreshock-mainshock, mainshock-aftershock) with short time and space separation. The first event of a pair should not be an aftershock, i.e., itmust not be related to a stronger previous event. The Italian earthquake catalog of the Istituto Nazionale di Geofisica (ING) (1975–1995, M > 3:4), the earthquake catalog of the Japan Meteorological Agency (JMA) (1983– 1994, M > 3:0) and that of the National Observatory of Athens (NOA) (1982–1994, M > 3:8) were analyzed. The number of observed pairs depends on several parameters: the size of the space-time quiescence volume defining nonaftershocks, the inter event time, the minimum magnitude of the two events, and the spatial dimension of the alarm volume after the first event. The Akaike information criterion has been adopted to assess the optimum set of space-time parameters used in the definition of the pairs, assuming that the occurrence rate of subsequent events may be modeled by two Poisson processes with different rates: the higher rate refers to the space-time volume defined by the alarms and the lower one simulates earthquakes that occur in the nonalarm space-time volume. On the basis of the tests carried out on the seismic catalog of Italy, the occurrence rate of M > 3:8 earthquakes followed by a M > 3:8 mainshock within 10 km and 10 days (validity) is 0.459. We have observed, for all three catalogs, that the occurrence rate density for the second event of a couple (mainshock or aftershock) of magnitude M2 subsequent to a non aftershock of magnitude M1 in the time range T can be modeled by the following relationship: .T , M2/ D 10a 0Cb.M1M2/ with b varying from 0.74 (Japan) to 1.09 (Greece). The decrease of the occurrence rate in time for a mainshock after a foreshock or for large aftershocks after a mainshock, for all three databases, obeys the Omori’s law with p changing from 0.94 (Italy) to 2.0 (Greece).164 21 - PublicationOpen AccessSeismicity Models for Moderate Earthquakes in Kanto, Central Japan(2007-05-31)
; ;Imoto, M.; National Research Institute for Earth Science and Disaster Prevention, Japan; ; ; ; ;Cocco, Massimo; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Console, Rodolfo; INGV, Rome, Italy ;Wiemer, Stefan; ETH, Zurich, Switzerland; ; Seismicity Models for Moderate Earthquakes in Kanto, Central Japan117 139