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Originally posted by DamaSan
reply to post by kdog1982
Hard to know for sure, especially in that complicated seismic area... but I would think swarms and EQs that occur on the same spot with frequency then suddenly stopping. I'm sure the GESS/M8 guys have more sophisticated ways of discerning a possible foreshock from an isolated event. They have all sorts of toys and algorithms that we do not.
There has been a lot of newly developed concepts over the last few days. Worked all weekend, which is somewhat uncharacteristic without having a major event occurring.
The emphasis right now will take the form of a steady increase in PSA's in the region coupled with a lead up to what's called "The Great California Shake Out". You'll hear more, you'll see more, about this routine drill than you have ever before.
I'll keep you posted. The data I've seen, which is limited, is quite impressive. Leaps and bounds over previous research I have been privy to. They are expecting steady foreshocks over the next 30 days as well, so please be watching the regional S.C. area only. Quoted from today's MB, "people who are aware will begin to notice something is unusual".
this is an email exchange from my boss regarding some research from an organization that is connected to jpl in pasadena, ca. this place is a buzz right now with new info. i've had to protect identities so i x'd out names and emails, and i don't exactly know what the info is.
Title: EARTHQUAKE FORECASTING.
Author: Rhoades, David; Evison, Frank; Kozuch, Mike
Author Affiliation: Institute of Geological Nuclear Sciences, Lower Hutt, New Zealand.
Source: Tephra, volume 17, June 1998, pages 21-23. ISSN: 0112-1359
Table, maps. Journal published by the New Zealand Ministry of Civil Defense.
Countermeasures; Earthquake patterns; Earthquake prediction; Earthquake swarms;
Foreshocks; Hazard mitigation; New Zealand; Precursors; Seismic zoning
New Zealand's earthquake forecasting program focuses on precursory earthquake
patterns. A description is provided of the research process for identifying a
precursory pattern and using it for forecasting as it proceeds from the anecdotal
stage to experimental stage and finally to the operational stage. Results are briefly
described of one precursor pattern currently being tested in New Zealand, the
earthquake swarm. Choices of countermeasures based on long, intermediate and short
range forecasts are also presented.
Major Topics: Earthquake Prediction; Seismology; Socio-Economic Aspects of Disasters,
Preparedness and Relief
Publication Type: Journal article
Call Number: QUAKELINE: MCEER VF01463
Record ID: QKLN-2000-0178
Title: MODEL FOR INTERMEDIATE-TERM PRECURSORY CLUSTERING OF EARTHQUAKES.
Author: Yama#a, T.; Knopoff, L.
Author Affiliation: Earthquake Research Institute, Tokyo University, Tokyo, Japan.
Source: Journal of Geophysical Research, volume 97, number B13, December 10, 1992,
pages 19,873-19,879. ISSN: 0148-0227
48 references. Graphs, diagram. A publication of the American Geophysical Union.
Series: Paper number 92JB01216. Institute of Geophysics and Planetary Physics,
University of California, Los Angeles publication number 3815.
Aggregation model; Crack growth; Earthquake swarms; Foreshocks; Intermediate term
precursory clustering; Main shocks; Multiplanar earthquake fault system;
Quiescence; Rheological models
A casual sequence of an earthquake swarm, extended quiescence, foreshocks, and main
shock can be understood in terms of an aggregation model of crack growth and ultimate
fusion on a multiplanar earthquake fault system. The rheological model is one of
accelerated crack growth under conditions of slip weakening, coupled with a slow
recovery of static friction after fracture. Once a slip feature has been generated
that spans a large part of the available geometry, a stress shadow is cast on other,
neighboring cracks that strongly retards and inhibits crack growth, thus initiating
the quiescent phase abruptly. The success of the model depends on the assumption that
nonlinear rheology regulates the rate of slip and that earthquake faults are not
simply connected surfaces but instead have many strands. (Authors' abstract).
Major Topics: Seismology
Publication Type: Journal article
Call Number: QUAKELINE: SEL Per QC811.J8
Record ID: QKLN-1993-2217
Title: MECHANISM OF THE OCCURRENCE OF EARTHQUAKE PRECURSORS.
Author: Mogi, Kiyoo
Author Affiliation: College of Industrial Technology, Nihon University, Izumicho 1-2-1,
Narashino City, Chiba 275, Japan.
Source: Jishin (Zisin: Journal of the Seismological Society of Japan), volume 45,
number 1, March 1992, pages 61-69. ISSN: 0037-1114
18 references. Maps, diagrams, graphs. Articles include abstracts and figure captions
Earthquake swarms; Foreshocks; Mechanisms; Precursors; Prediction; Rupture
processes; Seismic gaps; Tectonics
The process of the occurrence of an earthquake is discussed from the mechanical point
of view. It is emphasized that the structural heterogeneity in and around the
earthquake source region is one of the most important factors which cause the
occurrence of precursory phenomena. Earthquake precursors are classified into the
following two types. The one is the precursors which are caused by the increase in
stress. In general, long-term precursors are those of this type. The gradual increase
of earthquake swarm activity before the 1983 Japan Sea earthquake, the gradual
increase in seismic activity in the surrounding region of the 1989 Loma Prieta
earthquake before the main shock and the appearance of the seismic gaps of the second
kind are discussed as examples of this type. The other is the precursors which are
caused by a slowly progressive rupture process just before the sudden main fracture.
Short-term precursors are mainly those of this type. Foreshocks prior to the 1934 and
1966 Parkfield earthquakes are discussed as the typical examples of this type.
Major Topics: Earthquake Prediction
Publication Type: Journal article
Call Number: QUAKELINE: SEL Per QE531.Z5
Record ID: QKLN-1993-0562
Title: Waveform and spectral features of earthquake swarms and foreshocks--in special
reference to earthquake prediction.
Author: Tsujiura, M.
Source: Bulletin of the Earthquake Research Institute, University of Tokyo, Vol.
58 Iss. 1, pp. 65-134; 1983.
Spectra » earthquake swarms; Spectra » foreshocks; Precursory phenomena » earthquake
The author analyzes waveforms and spectra for earthquake swarms, foreshocks, and
ordinary seismic activities. These analyses reveal certain differences in the activity
modes of these types of events, the most striking of which is in the similarities of
waveforms for each group. Swarm activity, occurring in a certain short time interval,
mainly consists of events with similar waveforms, belonging to an event group called
an earthquake family. Foreshock activity, on the other hand, consists of events with
individual waveform characteristics, and in ordinary seismic activity the rate of
occurrence of earthquake families is also very low. Considering swarms as earthquake
families, the author points out other differences between their activity modes and
those of foreshock and ordinary seismic activity. These include differences in
epicenter distribution, source spectra, and corner frequencies. The author discusses
the significance of these differences and suggests possible diagnostic applications.
Major Topics: Seismology -- Earthquake Prediction
Publication Type: Journal article
Call Number: EEA: 250/T63/v.58(1)
Record ID: EEA-131000182
Database: EARTHQUAKE ENGINEERING ABSTRACTS
InSAR is one way to forecast quakes, but perhaps not the only one. While InSAR satellites merely improve the data available to orthodox seismology, there are other techniques that break with orthodoxy.
One of these ideas is to look for surges in infrared (IR) radiation.
What causes rocks under pressure to emit infrared radiation? No one is certain. The frequency spectrum of the emissions shows that internal heat from friction--e.g., rocks rubbing together--is not responsible for the radiation.
In one laboratory experiment, Freund and colleagues placed red granite blocks under a 1,500 ton press--mimicking in some ways what happens miles below Earth's surface. A sensitive camera developed at JPL and GSFC monitored the rock and detected infrared emissions. Furthermore, a voltage built up on the rock's surface. This leads Freund to believe the cause might be electrical.
Electrical currents in rock might explain another curious observation: Scientists doing research with magnetometers just before major earthquakes have serendipitously recorded tiny, slow fluctuations in Earth's magnetic field. One example happened during the Loma-Prieta earthquake that devastated San Francisco in 1989. Almost 2 weeks before the quake, readings of low-frequency magnetic signals (0.01-0.02 Hz) jumped up to 20 times above normal levels, and then spiked even higher the day of the quake.
The cause of these signals is unknown. In addition to Freund's idea, theories include the movement of deep, ion-conducting groundwater into cracks opened up by the crushing of rocks, electromagnetic energy released by electrons that are sheered from crystalline rocks such as granite, and a piezo-magnetic effect triggered by pressure applied to certain kinds of rocks.
Both the infrared and magnetic methods of quake detection are controversial. For now InSAR seems to be a safer bet for earthquake forecasting. All three, however, offer a tantalizing possibility: Someday the local weather report will forecast not only of the storms above us, but also the ones brewing beneath our feet.
The finding comes from an analysis of the seismic record from the lead-up to a devastating earthquake that hit Turkey in 1999. This revealed that foreshocks rippled away from the source of the rupture in the 45 minutes before the quake – the first time that foreshocks have been conclusively linked to a major earthquake. source
In the paper, we analyze 117 moderate-strong earthquakes occurred in Chinese mainland (M S≥5.5 in the east and M S≥6.0 in the west) since 1970, among them, 11 earthquakes (about 9%) have direct foreshocks and 63 earthquakes (about 51%) have generalized foreshocks. The predominant time interval between foreshock and main earthquake is no more than 30 days with a spatial distance less than 50 km and a magnitude difference over 1. From the digital seismic data in liaoning Province, we know that direct foreshock had an obvious shear-stress background before the M S=5.6 and M S=5.1 Xiuyan earthquakes occurred on Nov. 29, 1999 and Jan.15, 2000. source
Earthquake clusterings in both space and time have various forms, in particular, two typical examples are the foreshock sequences and earthquake swarms. Based on the analysis of 8 foreshock sequences in mainland China during 1966–1996, this study concentrates on the pattern characteristics of foreshock sequences. The following pattern characteristics of foreshock sequences have been found (1) the epicenters of foreshock sequences were densely concentrated in space; (2) the focal mechanisms of foreshocks were similar to that of the main shock. Such consistency of focal mechanisms with main shocks did not exist in aftershock series as well as in several earthquake swarms; (3) we found no case in mainland China during the past thirty years that a main shock is preceded by an earthquake clustering with inconsistent focal mechanisms. Finally, we found 5% of the main shocks in mainland China are preceded by foreshock sequences. source
2001 source The spectral analysis of waveforms from moderate and weak earthquakes in the Kurile-Kamchatka region allows one to rather reliably discriminate between foreshocks of forthcoming strong events and independent swarms of seismic shocks. Anomalously high frequencies of seismic radiation from foreshock sources are due to an anomalous rigidity of the seismogenic medium. Based on significant frequency anomalies determined from seismic records of foreshock sequences, the methods developed by the authors can be applied to recognize medium- and short-term seismological precursory effects.