Detailed Analysis of Seismograms and Earthquake Phenomena

This report summarizes the analysis of seismograms, emphasizing their crucial role in understanding earthquakes and the Earth's interior. It discusses how seismograms provide quantitative data about seismic sources, including magnitude, frequency, and rupture processes. The report delves into global seismicity patterns, seismic gaps, and the use of thrust mechanisms to analyze large earthquakes, and also explores the occurrences of false events. Furthermore, it examines the rupture process of large earthquakes, regional seismotectonics, and the determination of seismic moments for both recent and historical events. The study also highlights the importance of strong motion seismology and addresses unusual events like tsunami earthquakes. The analysis covers various aspects of seismology, providing a comprehensive overview of earthquake-related phenomena and the methods used to study them.

Summarization of the paper
Seismograms are used to produce the basic quantitative information about the seismic source and
the interior of the earth. By using seismographic instruments we can get wide dynamic range of
seismograms with quality frequency band. seismographic instruments consists of a mass
attached to a fixed base. When earth quake occurs base will be move and the mass does not, it
remains the same position. The motion of the base with respect to the mass is commonly
transformed into an electrical voltage. Seismograms analysis used to find the Earth's interior and
physics of earthquakes ,by improving magnitude quantity and quality. In the last 80 years about
10 earthquakes are occurred larger than surface wave magnitude (Ms)7 in the world.
Global seismicity
From the table of values given in the paper It is clear that the values of Ms is most significant to
discuss about global seismicity. From those tables we can understand that global seismic activity
is non uniform with respect to time. Because of these factors we need a data of seismicity over a
long period of time is most important.The magnitude and frequency relation of earth quakes are
analyzed over different years.
Thurst mechanism is applied to analyse the most of the large earth quakes in the subduction
zones. very large false event occurrences also notable.The sanriku earthquake 1933 and
Sumbawa earthquake 1977 is examples of false event occurrences. false event defines the failure
with in oceanic plate whereas thurst event defines the slip between the plate boundaries.earth
quake potential of seismic graphs are evaluated using thurst events and normal failure events.
Rupture process of large earthquakes
Rupture process is also a one of the important research subject to find out the large earth quakes
in the instrumental seismology.Long period sesimograms of large subduction zone earthquakes
to study the regional variations of the nature of subduction zones.In 1906 rupture process is
investigated in san Francisco earthquake by boore using ewing seismographs.From the arrival
time of P and S waves and their amplitudes at Mt.hamilton with in 35 km of the san Andreas
fault.

Seismic gaps
Seismic gaps also referred as a one of the natural earth quake which have occurred in the gap.In
this events are same in size and can be considered as a characteristic events.This can be find in
the basis of parkfield earth quake prediction experiment currently conducted in California. One
important feature of this subduction zone is very young subducting juan de foca plate.To
determine the aftershock area of the earthquake many Mexican station are examined ad from that
we can say, large earth quake did not occur at a subduction zone very similar to the june de fuca
boundary.
Regional sesimotectonics
Sesimotectonics of various regions can be effectively studied by historical
sesimograms.sesimicity data with relatively long period of time is needed to investigate the
pattern of current tectonic activity or to evaluate long term seismic risk in a certain region. But
high quality regional data are not available for old years, by using recent computational methods
of synthetic sesimograms we made this possible.To analyze the sesimograms recordings at
various distances, various methods are available.
Moment deterimination of old events
The data available for most large events that occurred after 1960,relatively accurate
determination of seismic moments has been made, where as accurate moments are not available
for a years prior to 1960.If relatively complete datasets of sesimograms of old years are available
this type of study can be made more easily and throuhly.
Strong motion seismology
Strong motion records from historical earth quakes are very important to estimate the amplitude
of strong ground motion. some long period strong motion seismographs developed in the early
days of seismology which is used to estimate the gross rise time of fault motion.
Tsunami earth quakes and other unusual events
Aleutian islands earth quakes generated very large tsunamis despite their relatively small earth
quake magnitude about 7.5 to 8. Several mechanisms are proposed but still the problem remains

unsolved. A few sesimograms of the 1980 siberian explosion consists of an air explosion at the
height of 8.5 km and a ballistic wave.