Modern seismic instruments

Slides:



Advertisements
Similar presentations
Transistors (MOSFETs)
Advertisements

Frequency modulation and circuits
Seismometry Seismic networks Instruments Mainly based on: Shearer, P.M., Introduction to seismology, Cambridge University Press, Lay, T., and T.C.
AN INERTIAL ROTATION METER (TILTMETER) Hutt, C. R., Holcomb, L. G., and Sandoval, L. D. USGS Albuquerque Seismological Laboratory Surface tilt noise has.
Variable Capacitance Transducers The Capacitance of a two plate capacitor is given by A – Overlapping Area x – Gap width k – Dielectric constant Permitivity.
Data Acquisition Risanuri Hidayat.
Principles of Electronic Communication Systems
International Training Course, Potsdam ORFEUS Workshop, Vienna IRIS Metadata Workshop, Cairo 2009 IRIS Metadata Workshop, Foz do Iguacu 2010 E. Wielandt:
© G. Washington, Seismic Transducers A seismic transducer consists of two basic components: i.Spring – Mass – Damper Element ii.Displacement Transducer.
Data centres and observablesModern Seismology – Data processing and inversion 1 Data in seismology: networks, instruments, current problems  Seismic networks,
Seismic sensors in PACMAN
Lecture #19- Seismometers
1 Chapter 5 Sensors and Detectors A detector is typically the first stage of a communication system. Noise in this stage may have significant effects on.
Lecture 31 Electrical Instrumentation. Lecture 32 Electrical Instrumentation Electrical instrumentation is the process of acquiring data about one or.
Lecture161 Instrumentation Prof. Phillips March 14, 2003.
Aloha Proof Module Design Cabled Observatory Presentation School of Ocean and Earth Science and Technology February 2006.
Ksjp, 7/01 MEMS Design & Fab Sensors Resistive, Capacitive Strain gauges, piezoresistivity Simple XL, pressure sensor ADXL50 Noise.
1/25/07184 Lecture 111 PHY 184 Spring 2007 Lecture 11 Title: Capacitors.
Principles of Electronic Communication Systems
Chapter 6 FM Circuits.
Chapter 7 Sound Recording and Reproduction
Metra Mess- und Frequenztechnik Radebeul / Germany Piezoelectric Accelerometers Theory & Application.
Introduction to seismic sensors (subject 3.2) Peter Novotny PACMAN meeting, CERN, 7 October 2014.
Trends in seismic instrumentation Based on the book Instrumentation in Earthquake Seismology Jens Havskov, Institute of Solid Earth Physics University.
EKT314/4 Electronic Instrumentation
Seismicity around Lhasa Tsoja Wangmo 1), Norsang Gelsor 1) and Jens Havskov 2) 1) Jiangsu Road No 36 Lhasa, Tibet, PRC 2) University of Bergen, Department.
Idaho National Engineering and Environmental Laboratory Upgrade of INEEL Seismic Stations and Strong Motion Accelerographs to Digital Field Acquisition.
Esci 411, Advanced Exploration Geophysics (Micro)seismicity John Townend EQC Fellow in Seismic Studies
Judah Levine, NIST, Mar-2006: 1 Using g to monitor the snow pack Judah Levine John Wahr Department of Physics University of Colorado
Seismology Part IX: Seismometery. Examples of early attempts to record ground motion.
An Affordable Broadband Seismometer : The Capacitive Geophone
DATA ACQUISITION Today’s Topics Define DAQ and DAQ systems Signals (digital and analogue types) Transducers Signal Conditioning - Importance of grounding.
Communication presented at the WORKSHOP High Quality Seismic Stations and Networks for Small Budgets Volcan, Panama March 2004 by Jens Havskov, Department.
Slide # 1 Velocity sensor Specifications for electromagnetic velocity sensor Velocity sensors can utilize the same principles of displacement sensor, and.
Geology 5660/6660 Applied Geophysics 17 Jan 2014 © A.R. Lowry 2014 Read for Wed 22 Jan: Burger (Ch 2.2–2.6) Last time: The Wave Equation; The Seismometer.
Seismometry Seismology and the Earth’s Deep Interior Seismometer – The basic Principles u x x0x0 ugug umum xmxm x x0x0 xrxr uground displacement x r displacement.
New earthquake category Nature 447, (3 May 2007) | doi: /nature05780; Received 8 December 2006; Accepted 26 March A scaling law for slow.
General Licensing Class Oscillators & Components Your organization and dates here.
Introduction to Engineering Lab 4 – 1 Basic Data Systems & Circuit Prototyping Agenda REVIEW OF LAB 3 RESULTS DEFINE a DATA SYSTEM  MAJOR TYPES  ELEMENTS.
Cuban Seismic Network National Centre for Seismological Research (2010) Ing. Eduardo R. Diez Zaldívar. Centro Nacional de Investigaciones Sismológicas.
RESOLVING FOCAL DEPTH WITH A NEAR FIELD SINGLE STATION IN SPARSE SEISMIC NETWORK Sidao Ni, State Key Laboratory of Geodesy and Earth’s Dynamics, Institute.
Mr.Santosh Kumar Scientist Web:
Z B Zhou, Y Z Bai, L Liu, D Y Tan, H Yin Center for Gravitational Experiments, School of Physics, Huazhong University of Science.
McGraw-Hill © 2008 The McGraw-Hill Companies, Inc. All rights reserved. Principles of Electronic Communication Systems FM Circuits.
Capacitive transducer. We know that : C=kЄ° (A/d) Where : K=dielectric constant Є° =8.854 *10^-12 D=distance between the plates A=the area over lapping.
A NON-TRADITIONAL HIGH PERFORMANCE BROAD-BAND SEISMOMETER PMD/eentec, USA
Seismic Arrays presented at the WORKSHOP High Quality Seismic Stations and Networks for Small Budgets Volcan, Panama March 2004by Jens Havskov, Department.
Teachers Name - Suman Sarker Subject Name Subject Name – Industrial Electronics (6832) Department Department – Computer (3rd) IDEAL INSTITUTE OF SCIENCE.
A Paper Presentation on VIBRATION MEASURING INSTRUMENTS by A.ARIF DEPARTMENT OF MECHANICAL ENGINEERING GUDLAVALLERU ENGINEERING COLLEGE GUDLAVALLERU -
The VIRGO Suspensions Control System Alberto Gennai The VIRGO Collaboration.
Small-aperture seismic arrays: instruments and detectability Jiří Málek, Milan Brož and Jaroslav Štrunc Institute of Rock Structure and Mechanics AS CR,
Geology 5660/6660 Applied Geophysics 20 Jan 2016
Instrumentation Symposium 10/9/2010 Nigbor 1 Instrumentation Selection Strategies Robert Nigbor
Signal Conditioning Elements (SCE). 6/13/2016Measurement & Transducers2 1. Voltage dividers Example :Potentiometer circuit.
Seismic instruments and seismic networks
4.2.3 Resonant filters. Following this session you should:- Recognise and sketch the characteristics for a simple band-pass filter; Be able to draw the.
Seismic phases and earthquake location
The Working Theory of an RC Coupled Amplifier in Electronics.
Lecture Notes / PPT UNIT III
FUNCTION GENERATOR.
MAGNITUDE SCALES FOR VERY LOCAL EARTHQUAKES. APPLICATION FOR DECEPTION ISLAND VOLCANO (ANTARCTICA). Jens Havskov(1,2), José A. Peña(2), Jesús M. Ibáñez(2,
MECH 373 Instrumentation and Measurements
MECH 373 Instrumentation and Measurements
AUTOMATIC STREET LIGHT CONTROL USING LDR
Variable Capacitance Transducers
REF TEK Technology Overview
Data Acquisition (DAQ)
Requirements, needs, wants:
Presentation transcript:

Modern seismic instruments presented at the seminar in honour of Peter Bormann Potsdam, September 2004 by Jens Havskov, Department of Earth Science University of Bergen Norway

Before: Seismographs were specially made Few standard components were used Very specialized software Now: Stations and networks are mainly made with standard industrial components Digital technology used throughout More standardized software Sensors currently the most specialized element Now possible to build a seismic station with mainly off the shelf products

Typical geophone SENSORS Trend is to use more broad band sensors (BB), even when overkill, however BB sensors now have a similar price as 1 Hz sensors 1 Hz sensors will go out except when used with feedback technique 4.5 Hz geophones the cheapest sensor, now used by several, either directly or with a feedback technique FBA based sensors will probably dominate the market in the future Typical geophone

M=5.5 quake at 300 km distance recorded with a 4.5Hz sensor Signal filtered 0.01 – 0.1 Hz

The FBA can have the digitizer integrated in feedback loop Spring Mass Volt out ~ Acceleration Force coil R Displacement transducer C Simplified principle behind Force Balanced Accelerometer. The displacement transducer normally uses a capacitor C, whose capacitance varies with the displacement of the mass. A current, proportional to the displacement transducer output, will force the mass to remain stationary relative to the frame. The FBA can have the digitizer integrated in feedback loop

13 cm The Kinemetrics 3-component Episensor, an FBA accelerometer

Kinemetrics Episensor internals

Left: The internals of the Güralp CMG-3T BB sensor Left: The internals of the Güralp CMG-3T BB sensor. Right: Sensor with digitizer. Photo’s supplied by Nathan Pearce, Güralp.

---------------- 2 mm ------------ Principal elements of a MEMS (micro electro mechanical systems) accelerometer with capacitive transducer. The mass is the upper mobile capacitor plate which can rotate around the torsion bars. The displacement, proportional to acceleration, is sensed with the variance in the capacitance. For high sensitive applications, a feedback circuit is added which controls a restoring electrostatic force, thus we have a FBA. The size of the sensor above is about 2 mm. Figure from www.silicondesigns.com/tech.html.

A simplified schematic of the electrochemical motion transducer used in MET seismometers (modified from R. Leugoud –PMD Scientific, Inc.-, 2003, personal communication). The electrolyte fluid is free to move in a channel. A set of platinum electrodes creates an ion concentration gradient by a small DC voltage. When the fluid moves due to acceleration, an additional current proportional to fluid velocity flows past the electrodes. The symmetric arrangement improves the linearity. The seismometer may operate with feedback to shape the response and increase linearity and dynamic range.

Different sensors at Univeristy of Bergen vault

Raw traces for different sensors A small window of the common traces for Z-channels. The numbers above the traces to the right are max amplitude in counts and the numbers to the left, the DC offset in counts.

Displacement 1-20 Hz A small window of the common traces for the Z-channels. The traces have been corrected for instrument response and show displacement in the frequency band 1-20 Hz. The numbers above the traces to the right are max amplitude in nm and the numbers to the left, the DC offset in nm. Notice that the last 3 traces are not from the same time window.

Displacement 0.2-1.0 Hz A small window of the common traces for the Z-channels. The traces have been corrected for instrument response and show displacement in the frequency band 0.2-1.0 Hz. The numbers above the traces to the right are max amplitude in nm and the the numbers to the left, the DC offset in nm

Acceleration and displacement Acceleration and displacement. The seismograms in the figure show the first few seconds of a P-wave of a small earthquake. On the site there is also an accelerometer installed (A) next to the seismometer (S). The top traces show the original records in counts. The signal from the seismometer is similar to the accelerometer signal, but with higher frequency contents for this later, and the amplitudes are different. The middle traces show the two signals converted to accelerations and the bottom traces, converted to displacement (frequency band 1-20 Hz). The signals are now very similar and of the same amplitude.

Instrument sensitivity of several Geotech seismometers ranging from the short period S-13 to very broad band 54000 seismometer. The curves show input acceleration equivalent to sensor internal noise in dB relative to 1(ms-2)2/Hz . NLNM is the Peterson New Low Noise Model (Peterson, 1993). Slightly modified from Geotech home page, www.geoinst.com.

Predicted total noise equivalent acceleration of a standard electronic circuit with a 4.5 Hz geophone. The contribution from each element is shown and the Peterson noise curves are shown for reference. Thermal noise is the noise due to Brownian thermal motion of the mass, Johnson noise is caused by thermal fluctuation of the electrons within any dissipative element in the electronic circuit, voltage and current noises are generated within the amplifier. Figure from Barzilai et al (1998).

The equivalent ground acceleration noise spectrum for a digitizer with its input shorted, using a low-sensitivity virtual sensor of 4.5 Hz and G=30 V/(m/s). The record of the digitizer noise has been reduced to the equivalent ground motion using its response combined with an imaginary low-sensitivity sensor. The spectrum then shows the worst-case sensitivity for ground motion that can be achieved with this digitizer and sensor. Of course, a more sensitive sensor would give a lower equivalent ground noise. The smooth curves on top and bottom are the Peterson New Low-Noise and New High-Noise models, for reference.

Noise spectrum from instrument using 4 Noise spectrum from instrument using 4.5 Hz sensor, 16 bit digitizer located in Tibet. Soil site

Main units of a seismic recorder Main units of a seismic recorder. There are no flow arrows between the units since all can have 2 way communication. The GPS can be connected to the digitizer or the recorder. The power supply may be common for all elements or each may have its own regulator, but usually the power source is unique (e.g. a battery).

Jan Mayen station, Liberg

The current trend in the development of the different elements of the portable recorders is: Computer: Based on a standard computer and operating system: Linux seems to be the favorite operating system, but Windows NT/2000 is also used. Single board PC’s with low power consumption. Communication and data transfer: -RS232 Ethernet/TCP/IP USB + others Sample rate, dynamic range and sensitivity: Sample rates from 1-1000 Hz, Dynamic range of at least 22 bit LSB (least significant bit) resolution of 0.1 μV. Standard Data acquisition software Power consumption: Below 2 W.

PC104 computer 8 cm

Field equipment made by UiB

Mobile phone with internet, TCP/IP (56 kb), operating system and 0 Mobile phone with internet, TCP/IP (56 kb), operating system and 0.5 gb memory

13cm x 18cm x 34cm

Nanometrics Taurus, the next generation handheld recorder (25 x 15 x 6 cm). Power consumption 0.8 W. From Nanomtrics home page, www.nanometrics.ca.  

Use of a small seismic array Improved detection of weak signals Automatic detection of P and S-wave arrivals Determination of azimuth Automatic location Location of weak emergent arrivals like volcanic tremor Building a regional location capability in a small area

Determination of azimuth and apparent velocity with Chiriqui array

Simple seismic station for stations and arrays Simple seismic station for stations and arrays. The station uses 18 bit converter, 4,5 Hz geophone, ost EU 1000. Recording with PC.

b a d c

Deception Island Symbols of the earthquakes indicates the focal depth of the events: dots smaller than 1 km, crosses between 1 and 3 km and squares focal depth greater than 3 km. Note that most events are very close to the array.