**2.5.3 Future perspectives**

284 Earthquake Research and Analysis – Statistical Studies, Observations and Planning

der creation in Yerevan State University, based on created *"hybrid SM-3"* new seismographs, capable of providing LabVIEW environment-based data acquisition and processing (Fig.7).

Fig. 7. LabVIEW signals of our new *SFCO absolute-*position sensor-based inertial seismic detector (the *"hybrid SM-3"* seismograph) for different amplitude shakings, ranging from

25 to 250nm, at the background vibration of about 5nm (see inset on *top left*). Background-vibration LabVIEW signals of the *SFCO*- sensor based new inertial seismic detector. Experiments were conducted at the night time-period, to achieve as low as possible

environment and vibration of the earth's crust.

**2.5.2 Discussion** 

noise level at room temperature in a technique caused by the industrial rocking of an

Comparison of signal-to-noise ratios (at F1Hz), for new sensor (*flat-coil based SFCO sensor* (s/n)*flat-coil* is about 16kHz/(5-10Hz) 1600-3200) and for *SM-3* sensor ((s/n)*EMF-sensor*150V /(4-5V) 30-35) both operating in the same *"hybrid SM-3"* seismograph permits to conclude that the *SFCO* sensor is more sensitive by about 50-100 times (see Figs. 6a and 8). Besides, since the *SFCO* sensor allows detecting of *absolute-*position shifts (see Fig.4, low frequencies), it may enable to detect very beginnings of *quasi-*static deformations and oscillating processes in earth crust at very low frequencies in contrast to the traditional *EMF*based sensors, being used practically in all acting inertial seismometers of a different design. This is the case since *EMF-*sensor may not detect slowly passing processes – due to minor voltage arising in solenoid pick-up coils during the slow movements of a pendulum (Fig.1c). So, in order to effectively detect *quasi-*static deformations by the *SFCO* technology-based *absolute-*position sensor, one should build and use a properly vibrating mechanical pendulum (*with a mass as heavy as possible*, and *with as weak as possible restoring force of the mechanical part of pendulum*) something like to what is the case in Russian *SM-3* detector, but with less friction against the motion of a freely hanging pendulum. *EMF-*based sensor may not detect slow processes, at any case, since it is a velocity sensor. This all may become crucial for detection of low-order free oscillations of the earth crust, and for observation of the peculiari-

There are many ways how to even more enhance the resolution of such new *absolute-*position sensors, and, as a result, capabilities of the presently acting *inertial seismometers* even by the several orders of magnitude. For that purpose, the pick-up flat coil, and/or the active element of the measuring oscillator should be made of superconductive material (high-*T*c or low-*T*<sup>c</sup> for better stability). In other words, one of the relatively easier ways relates with

Fig. 11. The *SFCO-*sensor based *Early Warning Security System* can secure the ground and underground, as well as specific underwater perimeter with the invisible and totally passive

security net, and identify the location of underwater moving intruders.

the replacement of the normal-metallic coil by the superconductive one. This may improve the tunnel diode oscillator stability by at least 1-2 orders of magnitude [2]. The next improvement relates with the substitution of the tunnel diode by the superconductive *S/I/S* hetero-structure as much more less-powered active element (*compared to tunnel diodes*) for the measuring oscillator of the *SFCO absolute-*position sensor, with a few orders of magnitude less steep of its *I-V* curve's negative differential resistance [16]. This may raise the oscillator stability by another 2-3 orders of a value [2]. Even these two modernizations are enough in order to enhance the stability of the measuring and reference oscillators of such a technique (Fig.3) and hence, to increase the signal-to-noise ratio (*sensitivity*) of the *SFCO* technologybased seismic detectors – by at least 3-4 orders of a value. As follows from the Fig.5, the *absolute-*resolution of such a new sensor drops exponentially when a normal-conducting plate moves away from the coil face. This property of *SFCO* sensors makes easy adjustment of the sensitivity (*resolution*) of such a new position sensor, for various practical usages in future.
