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Fixing unit conventions for moment magnitude #134

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Merged
merged 3 commits into from
Jan 26, 2016
Merged

Fixing unit conventions for moment magnitude #134

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637f0fc
Fixed units on moment mag
kwschultz Jan 26, 2016
d2604af
Cleanup
kwschultz Jan 26, 2016
224dfde
Fixing MKS magnitude convention
kwschultz Jan 26, 2016
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11 changes: 6 additions & 5 deletions quakelib/src/QuakeLibIO.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -756,7 +756,7 @@ void quakelib::ModelWorld::create_section(std::vector<unsigned int> &unused_trac
double moment_magnitude = 4.0+log10(conv.sqm2sqkm(fault_area));

for (unsigned int i=0; i<elem_ids.size(); ++i) {
double max_slip = pow(10, (3.0/2.0)*(moment_magnitude+10.7))/(1e7*element(elem_ids[i]).lame_mu()*fault_area);
double max_slip = pow(10, (3.0/2.0)*(moment_magnitude+6.0))/(element(elem_ids[i]).lame_mu()*fault_area);
element(elem_ids[i]).set_max_slip(max_slip);
}
}
Expand Down Expand Up @@ -872,7 +872,8 @@ void quakelib::ModelWorld::create_faults(const std::string &taper_method) {
// Schultz: Adapted from Steve Ward's model, used in the EQSim comparison for UCERF2 model
void quakelib::ModelWorld::compute_stress_drops(const double &stress_drop_factor) {
std::map<UIndex, ModelElement>::iterator eit;
UIndex fault_id;
UIndex fault_id;
Conversion conv;
ModelFault this_fault;
double fault_area, fault_length, fault_width, char_magnitude, char_slip, R, nu, stress_drop;

Expand All @@ -886,8 +887,8 @@ void quakelib::ModelWorld::compute_stress_drops(const double &stress_drop_factor
fault_length = this_fault.length();
fault_width = fault_area/fault_length;

char_magnitude = 4.0+log10(fault_area*1e-6) + stress_drop_factor;
char_slip = pow(10, (3.0/2.0)*(char_magnitude+10.7))/(1e7*eit->second.lame_mu()*fault_area);
char_magnitude = 4.0+log10(conv.sqm2sqkm(fault_area)) + stress_drop_factor;
char_slip = pow(10, (3.0/2.0)*(char_magnitude+6.0))/(eit->second.lame_mu()*fault_area);

nu = 0.5*eit->second.lame_lambda()/(eit->second.lame_mu() + eit->second.lame_lambda());
R = sqrt(fault_width*fault_width + fault_length*fault_length);
Expand Down Expand Up @@ -2254,7 +2255,7 @@ int quakelib::ModelWorld::read_files_eqsim(const std::string &geom_file_name, co
double moment_magnitude = 4.0+log10(conv.sqm2sqkm(fault_areas[eit->section_id()]));

// Need to document where this scaling law comes from
double max_slip = pow(10, (3.0/2.0)*(moment_magnitude+10.7))/(1e7*(eit->lame_mu())*fault_areas[eit->section_id()]);
double max_slip = pow(10, (3.0/2.0)*(moment_magnitude+6.0))/((eit->lame_mu())*fault_areas[eit->section_id()]);

// Set the max slip for the current element
eit->set_max_slip(max_slip);
Expand Down
4 changes: 2 additions & 2 deletions quakelib/src/QuakeLibIO.h
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Expand Up @@ -898,7 +898,7 @@ namespace quakelib {
moment += it->_slip*it->_mu*it->_area;
}

_data._event_magnitude = (2.0/3.0)*log10(1e7*moment) - 10.7;
_data._event_magnitude = (2.0/3.0)*log10(moment) - 6.0;
}

//! Get the total amount a given block slipped during this event
Expand Down Expand Up @@ -930,7 +930,7 @@ namespace quakelib {
moment += getBlockMu(*it)*getEventSlip(*it)*getEventArea(*it);
}

return (2.0/3.0)*log10(1e7*moment) - 10.7;
return (2.0/3.0)*log10(moment) - 6.0;
}

//! Get the magnitude of the earthquake in this event.
Expand Down
2 changes: 1 addition & 1 deletion src/core/Simulation.h
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Expand Up @@ -233,7 +233,7 @@ class Simulation : public SimFramework, public VCParams, public VCSimData, publi

// Get current expected slip from the current event area
char_magnitude = 4.0+log10(current_event_area*1e-6) + stressDropFactor();
char_slip = pow(10, (3.0/2.0)*(char_magnitude+10.7))/(1e7*getBlock(gid).lame_mu()*current_event_area);
char_slip = pow(10, (3.0/2.0)*(char_magnitude+6.0))/(getBlock(gid).lame_mu()*current_event_area);

dynamicStressDrop = -2*getBlock(gid).lame_mu()*char_slip*( (1-nu)*fault_length/fault_width + fault_width/fault_length )/( (1-nu)*M_PI*R );

Expand Down
2 changes: 1 addition & 1 deletion src/simulation/RunEvent.cpp
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Expand Up @@ -811,7 +811,7 @@ void RunEvent::processAftershock(Simulation *sim) {

// Determine the amount of slip needed to match the aftershock magnitude
// The contribution of each block to moment is based on its fraction of total area*mu
double total_moment = pow(10, (as.mag + 10.7)*(3.0/2.0))/1e7;
double total_moment = pow(10, (as.mag + 6.0)*(3.0/2.0));

for (bit=id_set.begin(); bit!=id_set.end(); ++bit) {
Block &b=sim->getBlock(*bit);
Expand Down